diff --git a/pip/__init__.py b/pip/__init__.py
old mode 100755
new mode 100644
index 804dfa1c43f..99fa932637e
--- a/pip/__init__.py
+++ b/pip/__init__.py
@@ -29,8 +29,8 @@
 except ImportError:
     pass
 else:
-    if (sys.platform == "darwin" and
-            ssl.OPENSSL_VERSION_NUMBER < 0x1000100f):  # OpenSSL 1.0.1
+    # OpenSSL 1.0.1 on MacOS
+    if sys.platform == "darwin" and ssl.OPENSSL_VERSION_NUMBER < 0x1000100f:
         try:
             from pip._vendor.requests.packages.urllib3.contrib import (
                 securetransport,
@@ -51,7 +51,6 @@
     InsecureRequestWarning,
 )
 
-
 # assignment for flake8 to be happy
 
 # This fixes a peculiarity when importing via __import__ - as we are
@@ -157,7 +156,8 @@ def create_main_parser():
 
     pip_pkg_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
     parser.version = 'pip %s from %s (python %s)' % (
-        __version__, pip_pkg_dir, sys.version[:3])
+        __version__, pip_pkg_dir, sys.version[:3]
+    )
 
     # add the general options
     gen_opts = cmdoptions.make_option_group(cmdoptions.general_group, parser)
diff --git a/pip/basecommand.py b/pip/basecommand.py
index c2e3c34cad3..3692e7caac4 100644
--- a/pip/basecommand.py
+++ b/pip/basecommand.py
@@ -191,8 +191,8 @@ def main(self, args):
                 deprecation.RemovedInPip11Warning,
             )
 
-        # TODO: try to get these passing down from the command?
-        #      without resorting to os.environ to hold these.
+        # TODO: Try to get these passing down from the command without
+        #       resorting to os.environ to hold these?
 
         if options.no_input:
             os.environ['PIP_NO_INPUT'] = '1'
@@ -212,8 +212,8 @@ def main(self, args):
 
         try:
             status = self.run(options, args)
-            # FIXME: all commands should return an exit status
-            # and when it is done, isinstance is not needed anymore
+            # FIXME: All commands should return an exit status
+            #        and when it is done, isinstance is not needed anymore
             if isinstance(status, int):
                 return status
         except PreviousBuildDirError as exc:
@@ -242,13 +242,14 @@ def main(self, args):
             return UNKNOWN_ERROR
         finally:
             # Check if we're using the latest version of pip available
-            if (not options.disable_pip_version_check and not
-                    getattr(options, "no_index", False)):
-                with self._build_session(
-                        options,
-                        retries=0,
-                        timeout=min(5, options.timeout)) as session:
+            _no_index = getattr(options, "no_index", False)
+            if not options.disable_pip_version_check and not _no_index:
+                session = self._build_session(
+                    options, retries=0, timeout=min(5, options.timeout)
+                )
+                with session:
                     pip_version_check(session, options)
+
             # Avoid leaking loggers
             for handler in set(logging.root.handlers) - original_root_handlers:
                 # this method benefit from the Logger class internal lock
@@ -269,10 +270,12 @@ def populate_requirement_set(requirement_set, args, options, finder,
         #       requirement_set.require_hashes may be updated
 
         for filename in options.constraints:
-            for req in parse_requirements(
-                    filename,
-                    constraint=True, finder=finder, options=options,
-                    session=session, wheel_cache=wheel_cache):
+            parsed_constraints = parse_requirements(
+                filename,
+                constraint=True, finder=finder, options=options,
+                session=session, wheel_cache=wheel_cache
+            )
+            for req in parsed_constraints:
                 requirement_set.add_requirement(req)
 
         for req in args:
@@ -293,10 +296,11 @@ def populate_requirement_set(requirement_set, args, options, finder,
             )
 
         for filename in options.requirements:
-            for req in parse_requirements(
-                    filename,
-                    finder=finder, options=options, session=session,
-                    wheel_cache=wheel_cache):
+            parsed_reqs = parse_requirements(
+                filename, finder=finder, options=options, session=session,
+                wheel_cache=wheel_cache
+            )
+            for req in parsed_reqs:
                 requirement_set.add_requirement(req)
         # If --require-hashes was a line in a requirements file, tell
         # RequirementSet about it:
diff --git a/pip/baseparser.py b/pip/baseparser.py
index ea76a21afeb..93864b60fbb 100644
--- a/pip/baseparser.py
+++ b/pip/baseparser.py
@@ -203,6 +203,7 @@ def _update_defaults(self, defaults):
                 late_eval.add(option.dest)
                 opt_str = option.get_opt_string()
                 val = option.convert_value(opt_str, val)
+
                 # From take_action
                 args = option.callback_args or ()
                 kwargs = option.callback_kwargs or {}
@@ -214,6 +215,7 @@ def _update_defaults(self, defaults):
 
         for key in late_eval:
             defaults[key] = getattr(self.values, key)
+
         self.values = None
         return defaults
 
@@ -230,6 +232,7 @@ def get_default_values(self):
             if isinstance(default, string_types):
                 opt_str = option.get_opt_string()
                 defaults[option.dest] = option.check_value(opt_str, default)
+
         return optparse.Values(defaults)
 
     def error(self, msg):
diff --git a/pip/cache.py b/pip/cache.py
index 271c7c1df33..9f1815044a9 100644
--- a/pip/cache.py
+++ b/pip/cache.py
@@ -19,12 +19,11 @@
 class Cache(object):
     """An abstract class - provides cache directories for data from links
 
-
-        :param cache_dir: The root of the cache.
-        :param format_control: A pip.index.FormatControl object to limit
-            binaries being read from the cache.
-        :param allowed_formats: which formats of files the cache should store.
-            ('binary' and 'source' are the only allowed values)
+    :param cache_dir: The root of the cache.
+    :param format_control: A pip.index.FormatControl object to limit
+                           binaries being read from the cache.
+    :param allowed_formats: Which formats of files the cache should store.
+                            ('binary' and 'source' are the only allowed values)
     """
 
     def __init__(self, cache_dir, format_control, allowed_formats):
@@ -70,6 +69,7 @@ def _get_candidates(self, link, package_name):
         if can_not_cache:
             return []
 
+        # Check if the format of this cache is allowed to be used
         canonical_name = canonicalize_name(package_name)
         formats = pip.index.fmt_ctl_formats(
             self.format_control, canonical_name
diff --git a/pip/cmdoptions.py b/pip/cmdoptions.py
index 3f9db5ba5ad..a276234f9a3 100644
--- a/pip/cmdoptions.py
+++ b/pip/cmdoptions.py
@@ -52,7 +52,8 @@ def getname(n):
         fmt_ctl_no_binary(control)
         warnings.warn(
             'Disabling all use of wheels due to the use of --build-options '
-            '/ --global-options / --install-options.', stacklevel=2)
+            '/ --global-options / --install-options.', stacklevel=2
+        )
 
 
 ###########
@@ -64,7 +65,8 @@ def getname(n):
     '-h', '--help',
     dest='help',
     action='help',
-    help='Show help.')
+    help='Show help.'
+)
 
 isolated_mode = partial(
     Option,
@@ -72,10 +74,8 @@ def getname(n):
     dest="isolated_mode",
     action="store_true",
     default=False,
-    help=(
-        "Run pip in an isolated mode, ignoring environment variables and user "
-        "configuration."
-    ),
+    help='Run pip in an isolated mode, ignoring environment variables and '
+         'user configuration.'
 )
 
 require_virtualenv = partial(
@@ -85,7 +85,8 @@ def getname(n):
     dest='require_venv',
     action='store_true',
     default=False,
-    help=SUPPRESS_HELP)
+    help=SUPPRESS_HELP
+)
 
 verbose = partial(
     Option,
@@ -101,7 +102,8 @@ def getname(n):
     '-V', '--version',
     dest='version',
     action='store_true',
-    help='Show version and exit.')
+    help='Show version and exit.'
+)
 
 quiet = partial(
     Option,
@@ -109,9 +111,8 @@ def getname(n):
     dest='quiet',
     action='count',
     default=0,
-    help=('Give less output. Option is additive, and can be used up to 3'
-          ' times (corresponding to WARNING, ERROR, and CRITICAL logging'
-          ' levels).')
+    help='Give less output. Option is additive, and can be used up to 3 times'
+         '(corresponding to WARNING, ERROR, and CRITICAL logging levels).'
 )
 
 progress_bar = partial(
@@ -121,8 +122,9 @@ def getname(n):
     type='choice',
     choices=list(BAR_TYPES.keys()),
     default='on',
-    help='Specify type of progress to be displayed [' +
-         '|'.join(BAR_TYPES.keys()) + '] (default: %default)')
+    help='Specify type of progress to be displayed [{}] (default: %default)'
+         .format('|'.join(BAR_TYPES.keys()))
+)
 
 log = partial(
     Option,
@@ -139,7 +141,8 @@ def getname(n):
     dest='no_input',
     action='store_true',
     default=False,
-    help=SUPPRESS_HELP)
+    help=SUPPRESS_HELP
+)
 
 proxy = partial(
     Option,
@@ -147,7 +150,8 @@ def getname(n):
     dest='proxy',
     type='str',
     default='',
-    help="Specify a proxy in the form [user:passwd@]proxy.server:port.")
+    help="Specify a proxy in the form [user:password@]proxy.server:port."
+)
 
 retries = partial(
     Option,
@@ -156,7 +160,8 @@ def getname(n):
     type='int',
     default=5,
     help="Maximum number of retries each connection should attempt "
-         "(default %default times).")
+         "(default %default times)."
+)
 
 timeout = partial(
     Option,
@@ -165,7 +170,8 @@ def getname(n):
     dest='timeout',
     type='float',
     default=15,
-    help='Set the socket timeout (default %default seconds).')
+    help='Set the socket timeout (default %default seconds).'
+)
 
 skip_requirements_regex = partial(
     Option,
@@ -174,7 +180,8 @@ def getname(n):
     dest='skip_requirements_regex',
     type='str',
     default='',
-    help=SUPPRESS_HELP)
+    help=SUPPRESS_HELP
+)
 
 
 def exists_action():
@@ -188,7 +195,8 @@ def exists_action():
         action='append',
         metavar='action',
         help="Default action when a path already exists: "
-        "(s)witch, (i)gnore, (w)ipe, (b)ackup, (a)bort.")
+        "(s)witch, (i)gnore, (w)ipe, (b)ackup, (a)bort."
+    )
 
 
 cert = partial(
@@ -197,7 +205,8 @@ def exists_action():
     dest='cert',
     type='str',
     metavar='path',
-    help="Path to alternate CA bundle.")
+    help="Path to alternate CA bundle."
+)
 
 client_cert = partial(
     Option,
@@ -207,7 +216,8 @@ def exists_action():
     default=None,
     metavar='path',
     help="Path to SSL client certificate, a single file containing the "
-         "private key and the certificate in PEM format.")
+         "private key and the certificate in PEM format."
+)
 
 index_url = partial(
     Option,
@@ -218,7 +228,8 @@ def exists_action():
     help="Base URL of Python Package Index (default %default). "
          "This should point to a repository compliant with PEP 503 "
          "(the simple repository API) or a local directory laid out "
-         "in the same format.")
+         "in the same format."
+)
 
 
 def extra_index_url():
@@ -240,7 +251,8 @@ def extra_index_url():
     dest='no_index',
     action='store_true',
     default=False,
-    help='Ignore package index (only looking at --find-links URLs instead).')
+    help='Ignore package index (only looking at --find-links URLs instead).'
+)
 
 
 def find_links():
@@ -252,7 +264,8 @@ def find_links():
         metavar='url',
         help="If a url or path to an html file, then parse for links to "
              "archives. If a local path or file:// url that's a directory, "
-             "then look for archives in the directory listing.")
+             "then look for archives in the directory listing."
+    )
 
 
 def trusted_host():
@@ -263,7 +276,7 @@ def trusted_host():
         metavar="HOSTNAME",
         default=[],
         help="Mark this host as trusted, even though it does not have valid "
-             "or any HTTPS.",
+             "or any HTTPS."
     )
 
 
@@ -274,7 +287,7 @@ def trusted_host():
     dest="process_dependency_links",
     action="store_true",
     default=False,
-    help="Enable the processing of dependency links.",
+    help="Enable the processing of dependency links."
 )
 
 
@@ -286,7 +299,8 @@ def constraints():
         default=[],
         metavar='file',
         help='Constrain versions using the given constraints file. '
-        'This option can be used multiple times.')
+        'This option can be used multiple times.'
+    )
 
 
 def requirements():
@@ -297,7 +311,8 @@ def requirements():
         default=[],
         metavar='file',
         help='Install from the given requirements file. '
-        'This option can be used multiple times.')
+             'This option can be used multiple times.'
+    )
 
 
 def editable():
@@ -307,8 +322,8 @@ def editable():
         action='append',
         default=[],
         metavar='path/url',
-        help=('Install a project in editable mode (i.e. setuptools '
-              '"develop mode") from a local project path or a VCS url.'),
+        help='Install a project in editable mode (i.e. setuptools '
+             '"develop mode") from a local project path or a VCS url.'
     )
 
 
@@ -319,8 +334,8 @@ def editable():
     metavar='dir',
     default=src_prefix,
     help='Directory to check out editable projects into. '
-    'The default in a virtualenv is "<venv path>/src". '
-    'The default for global installs is "<current dir>/src".'
+         'The default in a virtualenv is "<venv path>/src". '
+         'The default for global installs is "<current dir>/src".'
 )
 
 
@@ -332,13 +347,15 @@ def _get_format_control(values, option):
 def _handle_no_binary(option, opt_str, value, parser):
     existing = getattr(parser.values, option.dest)
     fmt_ctl_handle_mutual_exclude(
-        value, existing.no_binary, existing.only_binary)
+        value, existing.no_binary, existing.only_binary
+    )
 
 
 def _handle_only_binary(option, opt_str, value, parser):
     existing = getattr(parser.values, option.dest)
     fmt_ctl_handle_mutual_exclude(
-        value, existing.only_binary, existing.no_binary)
+        value, existing.only_binary, existing.no_binary
+    )
 
 
 def no_binary():
@@ -351,7 +368,8 @@ def no_binary():
              "disable all binary packages, :none: to empty the set, or one or "
              "more package names with commas between them. Note that some "
              "packages are tricky to compile and may fail to install when "
-             "this option is used on them.")
+             "this option is used on them."
+    )
 
 
 def only_binary():
@@ -364,7 +382,8 @@ def only_binary():
              "disable all source packages, :none: to empty the set, or one or "
              "more package names with commas between them. Packages without "
              "binary distributions will fail to install when this option is "
-             "used on them.")
+             "used on them."
+    )
 
 
 cache_dir = partial(
@@ -390,7 +409,8 @@ def only_binary():
     dest='ignore_dependencies',
     action='store_true',
     default=False,
-    help="Don't install package dependencies.")
+    help="Don't install package dependencies."
+)
 
 build_dir = partial(
     Option,
@@ -405,7 +425,8 @@ def only_binary():
     '--ignore-requires-python',
     dest='ignore_requires_python',
     action='store_true',
-    help='Ignore the Requires-Python information.')
+    help='Ignore the Requires-Python information.'
+)
 
 install_options = partial(
     Option,
@@ -417,7 +438,8 @@ def only_binary():
          "command (use like --install-option=\"--install-scripts=/usr/local/"
          "bin\"). Use multiple --install-option options to pass multiple "
          "options to setup.py install. If you are using an option with a "
-         "directory path, be sure to use absolute path.")
+         "directory path, be sure to use absolute path."
+)
 
 global_options = partial(
     Option,
@@ -426,14 +448,16 @@ def only_binary():
     action='append',
     metavar='options',
     help="Extra global options to be supplied to the setup.py "
-         "call before the install command.")
+         "call before the install command."
+)
 
 no_clean = partial(
     Option,
     '--no-clean',
     action='store_true',
     default=False,
-    help="Don't clean up build directories.")
+    help="Don't clean up build directories."
+)
 
 pre = partial(
     Option,
@@ -441,7 +465,8 @@ def only_binary():
     action='store_true',
     default=False,
     help="Include pre-release and development versions. By default, "
-         "pip only finds stable versions.")
+         "pip only finds stable versions."
+)
 
 disable_pip_version_check = partial(
     Option,
@@ -450,7 +475,8 @@ def only_binary():
     action="store_true",
     default=False,
     help="Don't periodically check PyPI to determine whether a new version "
-         "of pip is available for download. Implied with --no-index.")
+         "of pip is available for download. Implied with --no-index."
+)
 
 
 # Deprecated, Remove later
@@ -471,12 +497,15 @@ def _merge_hash(option, opt_str, value, parser):
     try:
         algo, digest = value.split(':', 1)
     except ValueError:
-        parser.error('Arguments to %s must be a hash name '
-                     'followed by a value, like --hash=sha256:abcde...' %
-                     opt_str)
+        parser.error(
+            'Arguments to %s must be a hash name followed by a value, like '
+            '--hash=sha256:abcde...' % opt_str
+        )
     if algo not in STRONG_HASHES:
-        parser.error('Allowed hash algorithms for %s are %s.' %
-                     (opt_str, ', '.join(STRONG_HASHES)))
+        parser.error(
+            'Allowed hash algorithms for %s are %s.'
+            % (opt_str, ', '.join(STRONG_HASHES))
+        )
     parser.values.hashes.setdefault(algo, []).append(digest)
 
 
@@ -490,7 +519,8 @@ def _merge_hash(option, opt_str, value, parser):
     callback=_merge_hash,
     type='string',
     help="Verify that the package's archive matches this "
-         'hash before installing. Example: --hash=sha256:abcdef...')
+         'hash before installing. Example: --hash=sha256:abcdef...'
+)
 
 
 require_hashes = partial(
@@ -501,7 +531,8 @@ def _merge_hash(option, opt_str, value, parser):
     default=False,
     help='Require a hash to check each requirement against, for '
          'repeatable installs. This option is implied when any package in a '
-         'requirements file has a --hash option.')
+         'requirements file has a --hash option.'
+)
 
 
 ##########
diff --git a/pip/commands/check.py b/pip/commands/check.py
index d951f8e87d2..fade62cdbe5 100644
--- a/pip/commands/check.py
+++ b/pip/commands/check.py
@@ -22,14 +22,16 @@ def run(self, options, args):
             for requirement in missing_reqs_dict.get(dist.key, []):
                 logger.info(
                     "%s %s requires %s, which is not installed.",
-                    dist.project_name, dist.version, requirement.project_name)
+                    dist.project_name, dist.version, requirement.project_name
+                )
 
-            for requirement, actual in incompatible_reqs_dict.get(
-                    dist.key, []):
+            incompatible = incompatible_reqs_dict.get(dist.key, [])
+            for requirement, actual in incompatible:
                 logger.info(
                     "%s %s has requirement %s, but you have %s %s.",
                     dist.project_name, dist.version, requirement,
-                    actual.project_name, actual.version)
+                    actual.project_name, actual.version
+                )
 
         if missing_reqs_dict or incompatible_reqs_dict:
             return 1
diff --git a/pip/commands/completion.py b/pip/commands/completion.py
index 1c0744d23a4..acc0d962f00 100644
--- a/pip/commands/completion.py
+++ b/pip/commands/completion.py
@@ -58,19 +58,22 @@ def __init__(self, *args, **kw):
             action='store_const',
             const='bash',
             dest='shell',
-            help='Emit completion code for bash')
+            help='Emit completion code for bash'
+        )
         cmd_opts.add_option(
             '--zsh', '-z',
             action='store_const',
             const='zsh',
             dest='shell',
-            help='Emit completion code for zsh')
+            help='Emit completion code for zsh'
+        )
         cmd_opts.add_option(
             '--fish', '-f',
             action='store_const',
             const='fish',
             dest='shell',
-            help='Emit completion code for fish')
+            help='Emit completion code for fish'
+        )
 
         self.parser.insert_option_group(0, cmd_opts)
 
diff --git a/pip/commands/download.py b/pip/commands/download.py
index a33c6097a2d..015c19c8a21 100644
--- a/pip/commands/download.py
+++ b/pip/commands/download.py
@@ -63,7 +63,7 @@ def __init__(self, *args, **kw):
             dest='download_dir',
             metavar='dir',
             default=os.curdir,
-            help=("Download packages into <dir>."),
+            help="Download packages into <dir>."
         )
 
         cmd_opts.add_option(
@@ -71,8 +71,8 @@ def __init__(self, *args, **kw):
             dest='platform',
             metavar='platform',
             default=None,
-            help=("Only download wheels compatible with <platform>. "
-                  "Defaults to the platform of the running system."),
+            help="Only download wheels compatible with <platform>. "
+                 "Defaults to the platform of the running system.",
         )
 
         cmd_opts.add_option(
@@ -80,12 +80,12 @@ def __init__(self, *args, **kw):
             dest='python_version',
             metavar='python_version',
             default=None,
-            help=("Only download wheels compatible with Python "
-                  "interpreter version <version>. If not specified, then the "
-                  "current system interpreter minor version is used. A major "
-                  "version (e.g. '2') can be specified to match all "
-                  "minor revs of that major version.  A minor version "
-                  "(e.g. '34') can also be specified."),
+            help="Only download wheels compatible with Python interpreter "
+                 "version <version>. If not specified, then the current "
+                 "system interpreter minor version is used. "
+                 "A major version (e.g. '2') can be specified to match all "
+                 "minor revs of that major version. "
+                 "A minor version (e.g. '34') can also be specified."
         )
 
         cmd_opts.add_option(
@@ -93,11 +93,11 @@ def __init__(self, *args, **kw):
             dest='implementation',
             metavar='implementation',
             default=None,
-            help=("Only download wheels compatible with Python "
-                  "implementation <implementation>, e.g. 'pp', 'jy', 'cp', "
-                  " or 'ip'. If not specified, then the current "
-                  "interpreter implementation is used.  Use 'py' to force "
-                  "implementation-agnostic wheels."),
+            help="Only download wheels compatible with Python "
+                 "implementation <implementation>, e.g. 'pp', 'jy', 'cp', "
+                 " or 'ip'. If not specified, then the current interpreter "
+                 "implementation is used.  Use 'py' to force "
+                 "implementation-agnostic wheels."
         )
 
         cmd_opts.add_option(
@@ -105,17 +105,15 @@ def __init__(self, *args, **kw):
             dest='abi',
             metavar='abi',
             default=None,
-            help=("Only download wheels compatible with Python "
-                  "abi <abi>, e.g. 'pypy_41'.  If not specified, then the "
-                  "current interpreter abi tag is used.  Generally "
-                  "you will need to specify --implementation, "
-                  "--platform, and --python-version when using "
-                  "this option."),
+            help="Only download wheels compatible with Python "
+                 "abi <abi>, e.g. 'pypy_41'.  If not specified, then the "
+                 "current interpreter abi tag is used.  Generally "
+                 "you will need to specify --implementation, --platform and "
+                 "--python-version when using this option."
         )
 
         index_opts = cmdoptions.make_option_group(
-            cmdoptions.index_group,
-            self.parser,
+            cmdoptions.index_group, self.parser,
         )
 
         self.parser.insert_option_group(0, index_opts)
@@ -144,7 +142,7 @@ def run(self, options, args):
                 "--only-binary=:all: must be set and --no-binary must not "
                 "be set (or must be set to :none:) when restricting platform "
                 "and interpreter constraints using --python-version, "
-                "--platform, --abi, or --implementation."
+                "--platform, --abi or --implementation."
             )
 
         options.src_dir = os.path.abspath(options.src_dir)
@@ -173,10 +171,10 @@ def run(self, options, args):
                 )
                 options.cache_dir = None
 
-            with TempDirectory(
+            directory = TempDirectory(
                 options.build_dir, delete=build_delete, kind="download"
-            ) as directory:
-
+            )
+            with directory:
                 requirement_set = RequirementSet(
                     require_hashes=options.require_hashes,
                 )
@@ -217,9 +215,7 @@ def run(self, options, args):
                     req.name for req in requirement_set.successfully_downloaded
                 ])
                 if downloaded:
-                    logger.info(
-                        'Successfully downloaded %s', downloaded
-                    )
+                    logger.info('Successfully downloaded %s', downloaded)
 
                 # Clean up
                 if not options.no_clean:
diff --git a/pip/commands/freeze.py b/pip/commands/freeze.py
index e02fdcf8799..de59ea855ba 100644
--- a/pip/commands/freeze.py
+++ b/pip/commands/freeze.py
@@ -34,7 +34,8 @@ def __init__(self, *args, **kw):
             metavar='file',
             help="Use the order in the given requirements file and its "
                  "comments when generating output. This option can be "
-                 "used multiple times.")
+                 "used multiple times."
+        )
         self.cmd_opts.add_option(
             '-f', '--find-links',
             dest='find_links',
@@ -42,31 +43,36 @@ def __init__(self, *args, **kw):
             default=[],
             metavar='URL',
             help='URL for finding packages, which will be added to the '
-                 'output.')
+                 'output.'
+        )
         self.cmd_opts.add_option(
             '-l', '--local',
             dest='local',
             action='store_true',
             default=False,
             help='If in a virtualenv that has global access, do not output '
-                 'globally-installed packages.')
+                 'globally-installed packages.'
+        )
         self.cmd_opts.add_option(
             '--user',
             dest='user',
             action='store_true',
             default=False,
-            help='Only output packages installed in user-site.')
+            help='Only output packages installed in user-site.'
+        )
         self.cmd_opts.add_option(
             '--all',
             dest='freeze_all',
             action='store_true',
-            help='Do not skip these packages in the output:'
-                 ' %s' % ', '.join(DEV_PKGS))
+            help='Do not skip these packages in the output: %s'
+                 % ', '.join(DEV_PKGS)
+        )
         self.cmd_opts.add_option(
             '--exclude-editable',
             dest='exclude_editable',
             action='store_true',
-            help='Exclude editable package from output.')
+            help='Exclude editable package from output.'
+        )
 
         self.parser.insert_option_group(0, self.cmd_opts)
 
@@ -86,7 +92,8 @@ def run(self, options, args):
             isolated=options.isolated_mode,
             wheel_cache=wheel_cache,
             skip=skip,
-            exclude_editable=options.exclude_editable)
+            exclude_editable=options.exclude_editable
+        )
 
         for line in freeze(**freeze_kwargs):
             sys.stdout.write(line + '\n')
diff --git a/pip/commands/install.py b/pip/commands/install.py
index 6c7dab73e5d..23dca265b8b 100644
--- a/pip/commands/install.py
+++ b/pip/commands/install.py
@@ -88,21 +88,24 @@ def __init__(self, *args, **kw):
             help="Install to the Python user install directory for your "
                  "platform. Typically ~/.local/, or %APPDATA%\\Python on "
                  "Windows. (See the Python documentation for site.USER_BASE "
-                 "for full details.)")
+                 "for full details.)"
+        )
         cmd_opts.add_option(
             '--root',
             dest='root_path',
             metavar='dir',
             default=None,
             help="Install everything relative to this alternate root "
-                 "directory.")
+                 "directory."
+        )
         cmd_opts.add_option(
             '--prefix',
             dest='prefix_path',
             metavar='dir',
             default=None,
             help="Installation prefix where lib, bin and other top-level "
-                 "folders are placed")
+                 "folders are placed"
+        )
 
         cmd_opts.add_option(cmdoptions.build_dir())
 
@@ -136,13 +139,15 @@ def __init__(self, *args, **kw):
             dest='force_reinstall',
             action='store_true',
             help='When upgrading, reinstall all packages even if they are '
-                 'already up-to-date.')
+                 'already up-to-date.'
+        )
 
         cmd_opts.add_option(
             '-I', '--ignore-installed',
             dest='ignore_installed',
             action='store_true',
-            help='Ignore the installed packages (reinstalling instead).')
+            help='Ignore the installed packages (reinstalling instead).'
+        )
 
         cmd_opts.add_option(cmdoptions.ignore_requires_python())
 
@@ -236,10 +241,10 @@ def run(self, options, args):
                     options.cache_dir,
                 )
                 options.cache_dir = None
-
-            with TempDirectory(
+            directory = TempDirectory(
                 options.build_dir, delete=build_delete, kind="install"
-            ) as directory:
+            )
+            with directory:
                 requirement_set = RequirementSet(
                     target_dir=target_temp_dir.path,
                     pycompile=options.compile,
diff --git a/pip/commands/list.py b/pip/commands/list.py
index 2891362f545..fd52f541d34 100644
--- a/pip/commands/list.py
+++ b/pip/commands/list.py
@@ -43,37 +43,41 @@ def __init__(self, *args, **kw):
             '-o', '--outdated',
             action='store_true',
             default=False,
-            help='List outdated packages')
+            help='List outdated packages'
+        )
         cmd_opts.add_option(
             '-u', '--uptodate',
             action='store_true',
             default=False,
-            help='List uptodate packages')
+            help='List uptodate packages'
+        )
         cmd_opts.add_option(
             '-e', '--editable',
             action='store_true',
             default=False,
-            help='List editable projects.')
+            help='List editable projects.'
+        )
         cmd_opts.add_option(
             '-l', '--local',
             action='store_true',
             default=False,
-            help=('If in a virtualenv that has global access, do not list '
-                  'globally-installed packages.'),
+            help='If in a virtualenv that has global access, do not list '
+                 'globally-installed packages.'
         )
         self.cmd_opts.add_option(
             '--user',
             dest='user',
             action='store_true',
             default=False,
-            help='Only output packages installed in user-site.')
+            help='Only output packages installed in user-site.'
+        )
 
         cmd_opts.add_option(
             '--pre',
             action='store_true',
             default=False,
-            help=("Include pre-release and development versions. By default, "
-                  "pip only finds stable versions."),
+            help="Include pre-release and development versions. By default, "
+                 "pip only finds stable versions."
         )
 
         cmd_opts.add_option(
@@ -83,7 +87,7 @@ def __init__(self, *args, **kw):
             default="columns",
             choices=('legacy', 'columns', 'freeze', 'json'),
             help="Select the output format among: columns (default), freeze, "
-                 "json, or legacy.",
+                 "json or legacy.",
         )
 
         cmd_opts.add_option(
diff --git a/pip/commands/show.py b/pip/commands/show.py
index 92c6c78cd55..ff5e4a104d8 100644
--- a/pip/commands/show.py
+++ b/pip/commands/show.py
@@ -28,7 +28,8 @@ def __init__(self, *args, **kw):
             dest='files',
             action='store_true',
             default=False,
-            help='Show the full list of installed files for each package.')
+            help='Show the full list of installed files for each package.'
+        )
 
         self.parser.insert_option_group(0, self.cmd_opts)
 
@@ -39,10 +40,10 @@ def run(self, options, args):
         query = args
 
         results = search_packages_info(query)
-        if not print_results(
-                results, list_files=options.files, verbose=options.verbose):
-            return ERROR
-        return SUCCESS
+        successful = print_results(
+            results, list_files=options.files, verbose=options.verbose
+        )
+        return SUCCESS if successful else ERROR
 
 
 def search_packages_info(query):
@@ -102,8 +103,11 @@ def search_packages_info(query):
         feed_parser = FeedParser()
         feed_parser.feed(metadata)
         pkg_info_dict = feed_parser.close()
-        for key in ('metadata-version', 'summary',
-                    'home-page', 'author', 'author-email', 'license'):
+        _keys = (
+            'metadata-version', 'summary', 'home-page', 'author',
+            'author-email', 'license'
+        )
+        for key in _keys:
             package[key] = pkg_info_dict.get(key)
 
         # It looks like FeedParser cannot deal with repeated headers
@@ -161,4 +165,5 @@ def print_results(distributions, list_files=False, verbose=False):
                 logger.info("  %s", line.strip())
             if "files" not in dist:
                 logger.info("Cannot locate installed-files.txt")
+
     return results_printed
diff --git a/pip/commands/uninstall.py b/pip/commands/uninstall.py
index 8608f37cac0..3b3e31e0f2d 100644
--- a/pip/commands/uninstall.py
+++ b/pip/commands/uninstall.py
@@ -38,13 +38,16 @@ def __init__(self, *args, **kw):
             '-y', '--yes',
             dest='yes',
             action='store_true',
-            help="Don't ask for confirmation of uninstall deletions.")
+            help="Don't ask for confirmation of uninstall deletions."
+        )
 
         self.parser.insert_option_group(0, self.cmd_opts)
 
     def run(self, options, args):
         with self._build_session(options) as session:
             reqs_to_uninstall = {}
+
+            # Determine which requirements have been given
             for name in args:
                 req = InstallRequirement.from_line(
                     name, isolated=options.isolated_mode,
@@ -52,19 +55,20 @@ def run(self, options, args):
                 if req.name:
                     reqs_to_uninstall[canonicalize_name(req.name)] = req
             for filename in options.requirements:
-                for req in parse_requirements(
-                        filename,
-                        options=options,
-                        session=session):
+                parsed_reqs = parse_requirements(
+                    filename, options=options, session=session
+                )
+                for req in parsed_reqs:
                     if req.name:
                         reqs_to_uninstall[canonicalize_name(req.name)] = req
+
             if not reqs_to_uninstall:
                 raise InstallationError(
                     'You must give at least one requirement to %(name)s (see '
                     '"pip help %(name)s")' % dict(name=self.name)
                 )
+
             for req in reqs_to_uninstall.values():
-                req.uninstall(
-                    auto_confirm=options.yes, verbose=options.verbose != 0
-                )
+                verbose = options.verbose != 0
+                req.uninstall(auto_confirm=options.yes, verbose=verbose)
                 req.uninstalled_pathset.commit()
diff --git a/pip/commands/wheel.py b/pip/commands/wheel.py
index cc6476c27a5..fcc94f303ac 100644
--- a/pip/commands/wheel.py
+++ b/pip/commands/wheel.py
@@ -53,8 +53,8 @@ def __init__(self, *args, **kw):
             dest='wheel_dir',
             metavar='dir',
             default=os.curdir,
-            help=("Build wheels into <dir>, where the default is the "
-                  "current working directory."),
+            help="Build wheels into <dir>, where the default is the "
+                 "current working directory."
         )
         cmd_opts.add_option(cmdoptions.no_binary())
         cmd_opts.add_option(cmdoptions.only_binary())
@@ -63,7 +63,8 @@ def __init__(self, *args, **kw):
             dest='build_options',
             metavar='options',
             action='append',
-            help="Extra arguments to be supplied to 'setup.py bdist_wheel'.")
+            help="Extra arguments to be supplied to 'setup.py bdist_wheel'."
+        )
         cmd_opts.add_option(cmdoptions.constraints())
         cmd_opts.add_option(cmdoptions.editable())
         cmd_opts.add_option(cmdoptions.requirements())
@@ -79,14 +80,15 @@ def __init__(self, *args, **kw):
             action='append',
             metavar='options',
             help="Extra global options to be supplied to the setup.py "
-            "call before the 'bdist_wheel' command.")
+            "call before the 'bdist_wheel' command."
+        )
 
         cmd_opts.add_option(
             '--pre',
             action='store_true',
             default=False,
-            help=("Include pre-release and development versions. By default, "
-                  "pip only finds stable versions."),
+            help="Include pre-release and development versions. By default, "
+                 "pip only finds stable versions.",
         )
 
         cmd_opts.add_option(cmdoptions.no_clean())
@@ -113,9 +115,7 @@ def check_required_packages(self):
             "To fix this, run: pip install --upgrade setuptools>=0.8"
         )
         pkg_resources = import_or_raise(
-            'pkg_resources',
-            CommandError,
-            need_setuptools_message
+            'pkg_resources', CommandError, need_setuptools_message
         )
         if not hasattr(pkg_resources, 'DistInfoDistribution'):
             raise CommandError(need_setuptools_message)
@@ -139,9 +139,10 @@ def run(self, options, args):
             build_delete = (not (options.no_clean or options.build_dir))
             wheel_cache = WheelCache(options.cache_dir, options.format_control)
 
-            with TempDirectory(
+            directory = TempDirectory(
                 options.build_dir, delete=build_delete, kind="wheel"
-            ) as directory:
+            )
+            with directory:
                 requirement_set = RequirementSet(
                     require_hashes=options.require_hashes,
                 )
diff --git a/pip/compat.py b/pip/compat.py
index 08cf2a14fff..eed2af93b37 100644
--- a/pip/compat.py
+++ b/pip/compat.py
@@ -57,7 +57,8 @@ def backslashreplace_decode_fn(err):
         return u"".join(u"\\x%x" % c for c in raw_bytes), err.end
     codecs.register_error(
         "backslashreplace_decode",
-        backslashreplace_decode_fn)
+        backslashreplace_decode_fn
+    )
     backslashreplace_decode = "backslashreplace_decode"
 
 
@@ -86,7 +87,8 @@ def console_to_str(data):
     except UnicodeDecodeError:
         logger.warning(
             "Subprocess output does not appear to be encoded as %s" %
-            encoding)
+            encoding
+        )
         s = data.decode(encoding, errors=backslashreplace_decode)
 
     # Make sure we can print the output, by encoding it to the output
@@ -101,8 +103,9 @@ def console_to_str(data):
     # or doesn't have an encoding attribute. Neither of these cases
     # should occur in normal pip use, but there's no harm in checking
     # in case people use pip in (unsupported) unusual situations.
-    output_encoding = getattr(getattr(sys, "__stderr__", None),
-                              "encoding", None)
+    output_encoding = getattr(
+        getattr(sys, "__stderr__", None), "encoding", None
+    )
 
     if output_encoding:
         s = s.encode(output_encoding, errors="backslashreplace")
diff --git a/pip/download.py b/pip/download.py
index 424a8a4bf7f..76b1f8fcc5c 100644
--- a/pip/download.py
+++ b/pip/download.py
@@ -589,8 +589,9 @@ def written_chunks(chunks):
         url = link.url_without_fragment
 
     if show_progress:  # We don't show progress on cached responses
-        progress_indicator = DownloadProgressProvider(progress_bar,
-                                                      max=total_length)
+        progress_indicator = DownloadProgressProvider(
+            progress_bar, max=total_length
+        )
         if total_length:
             logger.info("Downloading %s (%s)", url, format_size(total_length))
         else:
@@ -652,20 +653,18 @@ def unpack_http_url(link, location, download_dir=None,
         # If a download dir is specified, is the file already downloaded there?
         already_downloaded_path = None
         if download_dir:
-            already_downloaded_path = _check_download_dir(link,
-                                                          download_dir,
-                                                          hashes)
+            already_downloaded_path = _check_download_dir(
+                link, download_dir, hashes
+            )
 
         if already_downloaded_path:
             from_path = already_downloaded_path
             content_type = mimetypes.guess_type(from_path)[0]
         else:
             # let's download to a tmp dir
-            from_path, content_type = _download_http_url(link,
-                                                         session,
-                                                         temp_dir.path,
-                                                         hashes,
-                                                         progress_bar)
+            from_path, content_type = _download_http_url(
+                link, session, temp_dir.path, hashes, progress_bar
+            )
 
         # unpack the archive to the build dir location. even when only
         # downloading archives, they have to be unpacked to parse dependencies
@@ -707,9 +706,9 @@ def unpack_file_url(link, location, download_dir=None, hashes=None):
     # If a download dir is specified, is the file already there and valid?
     already_downloaded_path = None
     if download_dir:
-        already_downloaded_path = _check_download_dir(link,
-                                                      download_dir,
-                                                      hashes)
+        already_downloaded_path = _check_download_dir(
+            link, download_dir, hashes
+        )
 
     if already_downloaded_path:
         from_path = already_downloaded_path
@@ -779,8 +778,9 @@ def request(self, host, handler, request_body, verbose=False):
         url = urllib_parse.urlunparse(parts)
         try:
             headers = {'Content-Type': 'text/xml'}
-            response = self._session.post(url, data=request_body,
-                                          headers=headers, stream=True)
+            response = self._session.post(
+                url, data=request_body, headers=headers, stream=True
+            )
             response.raise_for_status()
             self.verbose = verbose
             return self.parse_response(response.raw)
diff --git a/pip/exceptions.py b/pip/exceptions.py
index 0353329f4db..3f8cb1b1996 100644
--- a/pip/exceptions.py
+++ b/pip/exceptions.py
@@ -173,9 +173,9 @@ def body(self):
                        # In case someone feeds something downright stupid
                        # to InstallRequirement's constructor.
                        else getattr(self.req, 'req', None))
-        return '    %s --hash=%s:%s' % (package or 'unknown package',
-                                        FAVORITE_HASH,
-                                        self.gotten_hash)
+        return '    %s --hash=%s:%s' % (
+            package or 'unknown package', FAVORITE_HASH, self.gotten_hash
+        )
 
 
 class HashUnpinned(HashError):
@@ -233,12 +233,15 @@ def hash_then_or(hash_name):
             return chain([hash_name], repeat('    or'))
 
         lines = []
-        for hash_name, expecteds in iteritems(self.allowed):
+        for hash_name, expect in iteritems(self.allowed):
             prefix = hash_then_or(hash_name)
-            lines.extend(('        Expected %s %s' % (next(prefix), e))
-                         for e in expecteds)
-            lines.append('             Got        %s\n' %
-                         self.gots[hash_name].hexdigest())
+            lines.extend(
+                ('        Expected %s %s' % (next(prefix), e)) for e in expect
+            )
+            lines.append(
+                '             Got        %s\n'
+                % self.gots[hash_name].hexdigest()
+            )
             prefix = '    or'
         return '\n'.join(lines)
 
diff --git a/pip/index.py b/pip/index.py
index 5808b921a88..d0c31294852 100644
--- a/pip/index.py
+++ b/pip/index.py
@@ -253,14 +253,16 @@ def sort_path(path):
                 else:
                     logger.warning(
                         "Url '%s' is ignored: it is neither a file "
-                        "nor a directory.", url)
+                        "nor a directory.", url
+                    )
             elif is_url(url):
                 # Only add url with clear scheme
                 urls.append(url)
             else:
                 logger.warning(
                     "Url '%s' is ignored. It is either a non-existing "
-                    "path or lacks a specific scheme.", url)
+                    "path or lacks a specific scheme.", url
+                )
 
         return files, urls
 
diff --git a/pip/operations/check.py b/pip/operations/check.py
index eef0630fc0a..3855f34edbf 100644
--- a/pip/operations/check.py
+++ b/pip/operations/check.py
@@ -9,8 +9,7 @@ def check_requirements(installed_dists):
         if missing_reqs:
             missing_reqs_dict[dist.key] = missing_reqs
 
-        incompatible_reqs = list(get_incompatible_reqs(
-            dist, installed_dists))
+        incompatible_reqs = list(get_incompatible_reqs(dist, installed_dists))
         if incompatible_reqs:
             incompatible_reqs_dict[dist.key] = incompatible_reqs
 
diff --git a/pip/operations/freeze.py b/pip/operations/freeze.py
index 6772022fdef..7da3a7dd227 100644
--- a/pip/operations/freeze.py
+++ b/pip/operations/freeze.py
@@ -44,9 +44,10 @@ def freeze(
     for link in find_links:
         yield '-f %s' % link
     installations = {}
-    for dist in get_installed_distributions(local_only=local_only,
-                                            skip=(),
-                                            user_only=user_only):
+    installed_dists = get_installed_distributions(
+        local_only=local_only, skip=(), user_only=user_only
+    )
+    for dist in installed_dists:
         try:
             req = FrozenRequirement.from_dist(
                 dist,
@@ -71,18 +72,22 @@ def freeze(
         for req_file_path in requirement:
             with open(req_file_path) as req_file:
                 for line in req_file:
-                    if (not line.strip() or
-                            line.strip().startswith('#') or
-                            (skip_match and skip_match(line)) or
-                            line.startswith((
-                                '-r', '--requirement',
-                                '-Z', '--always-unzip',
-                                '-f', '--find-links',
-                                '-i', '--index-url',
-                                '--pre',
-                                '--trusted-host',
-                                '--process-dependency-links',
-                                '--extra-index-url'))):
+                    line_is_ignorable = (
+                        not line.strip() or
+                        line.strip().startswith('#') or
+                        (skip_match and skip_match(line)) or
+                        line.startswith((
+                            '-r', '--requirement',
+                            '-Z', '--always-unzip',
+                            '-f', '--find-links',
+                            '-i', '--index-url',
+                            '--pre',
+                            '--trusted-host',
+                            '--process-dependency-links',
+                            '--extra-index-url'
+                        ))
+                    )
+                    if line_is_ignorable:
                         line = line.rstrip()
                         if line not in emitted_options:
                             emitted_options.add(line)
@@ -189,7 +194,8 @@ def from_dist(cls, dist, dependency_links):
                     )
                 if not svn_location:
                     logger.warning(
-                        'Warning: cannot find svn location for %s', req)
+                        'Warning: cannot find svn location for %s', req
+                    )
                     comments.append(
                         '## FIXME: could not find svn URL in dependency_links '
                         'for this package:'
diff --git a/pip/operations/prepare.py b/pip/operations/prepare.py
index 8212b191b69..26fa8ff72f1 100644
--- a/pip/operations/prepare.py
+++ b/pip/operations/prepare.py
@@ -72,8 +72,7 @@ def prep_for_dist(self):
 class IsWheel(DistAbstraction):
 
     def dist(self, finder):
-        return list(pkg_resources.find_distributions(
-            self.req.source_dir))[0]
+        return list(pkg_resources.find_distributions(self.req.source_dir))[0]
 
     def prep_for_dist(self):
         # FIXME:https://github.com/pypa/pip/issues/1112
@@ -189,12 +188,12 @@ def _prepare_linked_requirement(self, req, resolver):
             # occurs when the script attempts to unpack the
             # build directory
             req.ensure_has_source_dir(self.build_dir)
+
             # If a checkout exists, it's unwise to keep going.  version
             # inconsistencies are logged later, but do not fail the
             # installation.
             # FIXME: this won't upgrade when there's an existing
             # package unpacked in `req.source_dir`
-            # package unpacked in `req.source_dir`
             if os.path.exists(os.path.join(req.source_dir, 'setup.py')):
                 raise PreviousBuildDirError(
                     "pip can't proceed with requirements '%s' due to a"
@@ -210,9 +209,8 @@ def _prepare_linked_requirement(self, req, resolver):
                 resolver.require_hashes
             )
             # We can't hit this spot and have populate_link return None.
-            # req.satisfied_by is None here (because we're
-            # guarded) and upgrade has no impact except when satisfied_by
-            # is not None.
+            # req.satisfied_by is None here (because we're guarded) and upgrade
+            # has no impact except when satisfied_by is not None.
             # Then inside find_requirement existing_applicable -> False
             # If no new versions are found, DistributionNotFound is raised,
             # otherwise a result is guaranteed.
@@ -224,11 +222,10 @@ def _prepare_linked_requirement(self, req, resolver):
             # than otherwise. (For example, we can raise VcsHashUnsupported
             # for a VCS URL rather than HashMissing.)
             if resolver.require_hashes:
-                # We could check these first 2 conditions inside
-                # unpack_url and save repetition of conditions, but then
-                # we would report less-useful error messages for
-                # unhashable requirements, complaining that there's no
-                # hash provided.
+                # We could check these first 2 conditions inside unpack_url
+                # and save repetition of conditions, but then we would report
+                # less-useful error messages for unhashable requirements,
+                # complaining that there's no hash provided.
                 if is_vcs_url(link):
                     raise VcsHashUnsupported()
                 elif is_file_url(link) and is_dir_url(link):
@@ -276,13 +273,11 @@ def _prepare_linked_requirement(self, req, resolver):
             except requests.HTTPError as exc:
                 logger.critical(
                     'Could not install requirement %s because of error %s',
-                    req,
-                    exc,
+                    req, exc,
                 )
                 raise InstallationError(
                     'Could not install requirement %s because of HTTP '
-                    'error %s for URL %s' %
-                    (req, exc, req.link)
+                    'error %s for URL %s' % (req, exc, req.link)
                 )
             abstract_dist = make_abstract_dist(req)
             abstract_dist.prep_for_dist()
@@ -304,8 +299,8 @@ def _prepare_linked_requirement(self, req, resolver):
                     resolver._set_req_to_reinstall(req)
                 else:
                     logger.info(
-                        'Requirement already satisfied (use '
-                        '--upgrade to upgrade): %s',
+                        'Requirement already satisfied '
+                        '(use --upgrade to upgrade): %s',
                         req,
                     )
         return abstract_dist
@@ -341,8 +336,8 @@ def _prepare_installed_requirement(self, req, resolver, skip_reason):
         """
         assert req.satisfied_by, "req should have been satisfied but isn't"
         assert skip_reason is not None, (
-            "did not get skip reason skipped but req.satisfied_by "
-            "is set to %r" % (req.satisfied_by,)
+            "did not get skip reason skipped but req.satisfied_by is set to %r"
+            % (req.satisfied_by,)
         )
         logger.info(
             'Requirement %s: %s (%s)',
diff --git a/pip/pep425tags.py b/pip/pep425tags.py
index e33b6ce0ed0..a23577da039 100644
--- a/pip/pep425tags.py
+++ b/pip/pep425tags.py
@@ -51,8 +51,11 @@ def get_impl_version_info():
     version."""
     if get_abbr_impl() == 'pp':
         # as per https://github.com/pypa/pip/issues/2882
-        return (sys.version_info[0], sys.pypy_version_info.major,
-                sys.pypy_version_info.minor)
+        return (
+            sys.version_info[0],
+            sys.pypy_version_info.major,
+            sys.pypy_version_info.minor
+        )
     else:
         return sys.version_info[0], sys.version_info[1]
 
@@ -70,8 +73,11 @@ def get_flag(var, fallback, expected=True, warn=True):
     val = get_config_var(var)
     if val is None:
         if warn:
-            logger.debug("Config variable '%s' is unset, Python ABI tag may "
-                         "be incorrect", var)
+            logger.debug(
+                "Config variable '%s' is unset, "
+                "Python ABI tag may be incorrect",
+                var
+            )
         return fallback()
     return val == expected
 
diff --git a/pip/req/req_file.py b/pip/req/req_file.py
index 8231c456f5b..e1153b7340e 100644
--- a/pip/req/req_file.py
+++ b/pip/req/req_file.py
@@ -77,9 +77,10 @@ def parse_requirements(filename, finder=None, comes_from=None, options=None,
     lines_enum = preprocess(content, options)
 
     for line_number, line in lines_enum:
-        req_iter = process_line(line, filename, line_number, finder,
-                                comes_from, options, session, wheel_cache,
-                                constraint=constraint)
+        req_iter = process_line(
+            line, filename, line_number, finder, comes_from, options, session,
+            wheel_cache, constraint=constraint
+        )
         for req in req_iter:
             yield req
 
@@ -131,7 +132,8 @@ def process_line(line, filename, line_number, finder=None, comes_from=None,
 
     # preserve for the nested code path
     line_comes_from = '%s %s (line %s)' % (
-        '-c' if constraint else '-r', filename, line_number)
+        '-c' if constraint else '-r', filename, line_number
+    )
 
     # yield a line requirement
     if args_str:
@@ -297,7 +299,5 @@ def skip_regex(lines_enum, options):
     skip_regex = options.skip_requirements_regex if options else None
     if skip_regex:
         pattern = re.compile(skip_regex)
-        lines_enum = filterfalse(
-            lambda e: pattern.search(e[1]),
-            lines_enum)
+        lines_enum = filterfalse(lambda e: pattern.search(e[1]), lines_enum)
     return lines_enum
diff --git a/pip/req/req_install.py b/pip/req/req_install.py
index 4aacb34b404..cb8cc57a0aa 100644
--- a/pip/req/req_install.py
+++ b/pip/req/req_install.py
@@ -399,7 +399,8 @@ def name(self):
     def setup_py_dir(self):
         return os.path.join(
             self.source_dir,
-            self.link and self.link.subdirectory_fragment or '')
+            self.link and self.link.subdirectory_fragment or ''
+        )
 
     @property
     def setup_py(self):
@@ -475,7 +476,8 @@ def run_egg_info(self):
                 egg_info_cmd + egg_base_option,
                 cwd=self.setup_py_dir,
                 show_stdout=False,
-                command_desc='python setup.py egg_info')
+                command_desc='python setup.py egg_info'
+            )
 
         if not self.req:
             if isinstance(parse_version(self.pkg_info()["Version"]), Version):
@@ -529,24 +531,25 @@ def egg_info_path(self, filename):
                     # Iterate over a copy of ``dirs``, since mutating
                     # a list while iterating over it can cause trouble.
                     # (See https://github.com/pypa/pip/pull/462.)
-                    for dir in list(dirs):
+                    for dir_ in list(dirs):
                         # Don't search in anything that looks like a virtualenv
                         # environment
-                        if (
-                                os.path.lexists(
-                                    os.path.join(root, dir, 'bin', 'python')
-                                ) or
-                                os.path.exists(
-                                    os.path.join(
-                                        root, dir, 'Scripts', 'Python.exe'
-                                    )
-                                )):
-                            dirs.remove(dir)
+                        should_remove = (
+                            os.path.lexists(os.path.join(
+                                root, dir_, 'bin', 'python'
+                            )) or
+                            os.path.exists(os.path.join(
+                                root, dir_, 'Scripts', 'Python.exe'
+                            ))
+                        )
+                        if should_remove:
+                            dirs.remove(dir_)
                         # Also don't search through tests
-                        elif dir == 'test' or dir == 'tests':
-                            dirs.remove(dir)
-                    filenames.extend([os.path.join(root, dir)
-                                      for dir in dirs])
+                        elif dir_ == 'test' or dir_ == 'tests':
+                            dirs.remove(dir_)
+                    filenames.extend(
+                        [os.path.join(root, dir_) for dir_ in dirs]
+                    )
                 filenames = [f for f in filenames if f.endswith('.egg-info')]
 
             if not filenames:
@@ -716,7 +719,8 @@ def match_markers(self, extras_requested=None):
         if self.markers is not None:
             return any(
                 self.markers.evaluate({'extra': extra})
-                for extra in extras_requested)
+                for extra in extras_requested
+            )
         else:
             return True
 
@@ -725,7 +729,8 @@ def install(self, install_options, global_options=None, root=None,
         global_options = global_options if global_options is not None else []
         if self.editable:
             self.install_editable(
-                install_options, global_options, prefix=prefix)
+                install_options, global_options, prefix=prefix
+            )
             return
         if self.is_wheel:
             version = pip.wheel.wheel_version(self.source_dir)
@@ -749,7 +754,8 @@ def install(self, install_options, global_options=None, root=None,
         with TempDirectory(kind="record") as temp_dir:
             record_filename = os.path.join(temp_dir.path, 'install-record.txt')
             install_args = self.get_install_args(
-                global_options, record_filename, root, prefix)
+                global_options, record_filename, root, prefix
+            )
             msg = 'Running setup.py install for %s' % (self.name,)
             with open_spinner(msg) as spinner:
                 with indent_log():
@@ -834,9 +840,10 @@ def get_install_args(self, global_options, record_filename, root, prefix):
 
         if running_under_virtualenv():
             py_ver_str = 'python' + sysconfig.get_python_version()
-            install_args += ['--install-headers',
-                             os.path.join(sys.prefix, 'include', 'site',
-                                          py_ver_str, self.name)]
+            header_location = os.path.join(
+                sys.prefix, 'include', 'site', py_ver_str, self.name
+            )
+            install_args += ['--install-headers', header_location]
 
         return install_args
 
@@ -862,19 +869,14 @@ def install_editable(self, install_options,
             install_options = list(install_options) + prefix_param
 
         with indent_log():
-            # FIXME: should we do --install-headers here too?
-            call_subprocess(
-                [
-                    sys.executable,
-                    '-c',
-                    SETUPTOOLS_SHIM % self.setup_py
-                ] +
+            command = (
+                [sys.executable, '-c', SETUPTOOLS_SHIM % self.setup_py] +
                 list(global_options) +
                 ['develop', '--no-deps'] +
-                list(install_options),
-
-                cwd=self.setup_py_dir,
-                show_stdout=False)
+                list(install_options)
+            )
+            # FIXME: should we do --install-headers here too?
+            call_subprocess(command, cwd=self.setup_py_dir, show_stdout=False)
 
         self.install_succeeded = True
 
@@ -942,8 +944,8 @@ def get_dist(self):
         dist_name = os.path.splitext(os.path.basename(egg_info))[0]
         return pkg_resources.Distribution(
             os.path.dirname(egg_info),
-            project_name=dist_name,
-            metadata=metadata)
+            project_name=dist_name, metadata=metadata
+        )
 
     @property
     def has_hash_options(self):
diff --git a/pip/req/req_set.py b/pip/req/req_set.py
index 1c8a35e29a5..7151b663a8b 100644
--- a/pip/req/req_set.py
+++ b/pip/req/req_set.py
@@ -40,9 +40,8 @@ def __repr__(self):
 
 class RequirementSet(object):
 
-    def __init__(self,
-                 require_hashes=False, target_dir=None, use_user_site=False,
-                 pycompile=True):
+    def __init__(self, require_hashes=False, target_dir=None,
+                 use_user_site=False, pycompile=True):
         """Create a RequirementSet.
 
         :param wheel_cache: The pip wheel cache, for passing to
@@ -96,9 +95,10 @@ def add_requirement(self, install_req, parent_req_name=None,
         """
         name = install_req.name
         if not install_req.match_markers(extras_requested):
-            logger.warning("Ignoring %s: markers '%s' don't match your "
-                           "environment", install_req.name,
-                           install_req.markers)
+            logger.warning(
+                "Ignoring %s: markers '%s' don't match your environment",
+                install_req.name, install_req.markers
+            )
             return []
 
         # This check has to come after we filter requirements with the
@@ -125,13 +125,19 @@ def add_requirement(self, install_req, parent_req_name=None,
                 existing_req = self.get_requirement(name)
             except KeyError:
                 existing_req = None
-            if (parent_req_name is None and existing_req and not
-                    existing_req.constraint and
-                    existing_req.extras == install_req.extras and not
-                    existing_req.req.specifier == install_req.req.specifier):
+            already_given = (
+                parent_req_name is None and
+                existing_req and
+                not existing_req.constraint and
+                existing_req.extras == install_req.extras and
+                not existing_req.req.specifier == install_req.req.specifier
+            )
+            if already_given:
                 raise InstallationError(
                     'Double requirement given: %s (already in %s, name=%r)'
-                    % (install_req, existing_req, name))
+                    % (install_req, existing_req, name)
+                )
+
             if not existing_req:
                 # Add requirement
                 self.requirements[name] = install_req
@@ -144,21 +150,30 @@ def add_requirement(self, install_req, parent_req_name=None,
                 # encountered this for scanning.
                 result = []
                 if not install_req.constraint and existing_req.constraint:
-                    if (install_req.link and not (existing_req.link and
-                       install_req.link.path == existing_req.link.path)):
+                    cannot_have_constraint = (
+                        install_req.link and not (
+                            existing_req.link and
+                            install_req.link.path == existing_req.link.path
+                        )
+                    )
+                    if cannot_have_constraint:
                         self.reqs_to_cleanup.append(install_req)
                         raise InstallationError(
                             "Could not satisfy constraints for '%s': "
                             "installation from path or url cannot be "
-                            "constrained to a version" % name)
+                            "constrained to a version" % name
+                        )
+
                     # If we're now installing a constraint, mark the existing
                     # object for real installation.
                     existing_req.constraint = False
                     existing_req.extras = tuple(
                         sorted(set(existing_req.extras).union(
                                set(install_req.extras))))
-                    logger.debug("Setting %s extras to: %s",
-                                 existing_req, existing_req.extras)
+                    logger.debug(
+                        "Setting %s extras to: %s",
+                        existing_req, existing_req.extras
+                    )
                     # And now we need to scan this.
                     result = [existing_req]
                 # Canonicalise to the already-added object for the backref
@@ -171,17 +186,18 @@ def add_requirement(self, install_req, parent_req_name=None,
 
     def has_requirement(self, project_name):
         name = project_name.lower()
-        if (name in self.requirements and
-           not self.requirements[name].constraint or
-           name in self.requirement_aliases and
-           not self.requirements[self.requirement_aliases[name]].constraint):
-            return True
-        return False
+        return (
+            name in self.requirements and
+            not self.requirements[name].constraint or
+            name in self.requirement_aliases and
+            not self.requirements[self.requirement_aliases[name]].constraint
+        )
 
     @property
     def has_requirements(self):
-        return list(req for req in self.requirements.values() if not
-                    req.constraint) or self.unnamed_requirements
+        return list(
+            req for req in self.requirements.values() if not req.constraint
+        ) or self.unnamed_requirements
 
     def get_requirement(self, project_name):
         for name in project_name, project_name.lower():
@@ -227,8 +243,8 @@ def schedule(req):
 
     def install(self, install_options, global_options=(), *args, **kwargs):
         """
-        Install everything in this set (after having downloaded and unpacked
-        the packages)
+        Install everything in this set \
+        (after having downloaded and unpacked the packages)
         """
         to_install = self._to_install()
 
diff --git a/pip/req/req_uninstall.py b/pip/req/req_uninstall.py
index ca161e716e7..16e3170e599 100644
--- a/pip/req/req_uninstall.py
+++ b/pip/req/req_uninstall.py
@@ -193,8 +193,9 @@ def _stash(self, path):
         )
 
     def remove(self, auto_confirm=False, verbose=False):
-        """Remove paths in ``self.paths`` with confirmation (unless
-        ``auto_confirm`` is True)."""
+        """Remove paths in ``self.paths`` with confirmation \
+        (unless ``auto_confirm`` is True).
+        """
 
         if not self.paths:
             logger.info(
@@ -308,8 +309,8 @@ def from_dist(cls, dist):
             # are in fact in the develop_egg_link case
             paths_to_remove.add(dist.egg_info)
             if dist.has_metadata('installed-files.txt'):
-                for installed_file in dist.get_metadata(
-                        'installed-files.txt').splitlines():
+                lines = dist.get_metadata('installed-files.txt').splitlines()
+                for installed_file in lines:
                     path = os.path.normpath(
                         os.path.join(dist.egg_info, installed_file)
                     )
@@ -347,8 +348,9 @@ def from_dist(cls, dist):
             # i.e. setuptools-0.6c11-py2.6.egg vs setuptools-0.6rc11-py2.6.egg
             paths_to_remove.add(dist.location)
             easy_install_egg = os.path.split(dist.location)[1]
-            easy_install_pth = os.path.join(os.path.dirname(dist.location),
-                                            'easy-install.pth')
+            easy_install_pth = os.path.join(
+                os.path.dirname(dist.location), 'easy-install.pth'
+            )
             paths_to_remove.add_pth(easy_install_pth, './' + easy_install_egg)
 
         elif egg_info_exists and dist.egg_info.endswith('.dist-info'):
@@ -364,14 +366,16 @@ def from_dist(cls, dist):
                 '(at %s)' % (link_pointer, dist.project_name, dist.location)
             )
             paths_to_remove.add(develop_egg_link)
-            easy_install_pth = os.path.join(os.path.dirname(develop_egg_link),
-                                            'easy-install.pth')
+            easy_install_pth = os.path.join(
+                os.path.dirname(develop_egg_link), 'easy-install.pth'
+            )
             paths_to_remove.add_pth(easy_install_pth, dist.location)
 
         else:
             logger.debug(
                 'Not sure how to uninstall: %s - Check: %s',
-                dist, dist.location)
+                dist, dist.location
+            )
 
         # find distutils scripts= scripts
         if dist.has_metadata('scripts') and dist.metadata_isdir('scripts'):
diff --git a/pip/resolve.py b/pip/resolve.py
index 250b7313462..a3f8e607861 100644
--- a/pip/resolve.py
+++ b/pip/resolve.py
@@ -14,8 +14,8 @@
 from itertools import chain
 
 from pip.exceptions import (
-    BestVersionAlreadyInstalled,
-    DistributionNotFound, HashError, HashErrors, UnsupportedPythonVersion
+    BestVersionAlreadyInstalled, DistributionNotFound, HashError, HashErrors,
+    UnsupportedPythonVersion
 )
 from pip.req.req_install import InstallRequirement
 from pip.utils import dist_in_usersite, ensure_dir
diff --git a/pip/utils/__init__.py b/pip/utils/__init__.py
index e0091ebecac..c276cc8ceda 100644
--- a/pip/utils/__init__.py
+++ b/pip/utils/__init__.py
@@ -54,7 +54,8 @@
 ZIP_EXTENSIONS = ('.zip', '.whl')
 TAR_EXTENSIONS = ('.tar.gz', '.tgz', '.tar')
 ARCHIVE_EXTENSIONS = (
-    ZIP_EXTENSIONS + BZ2_EXTENSIONS + TAR_EXTENSIONS + XZ_EXTENSIONS)
+    ZIP_EXTENSIONS + BZ2_EXTENSIONS + TAR_EXTENSIONS + XZ_EXTENSIONS
+)
 SUPPORTED_EXTENSIONS = ZIP_EXTENSIONS + TAR_EXTENSIONS
 try:
     import bz2  # noqa
@@ -97,9 +98,10 @@ def get_prog():
 
 # Retry every half second for up to 3 seconds
 @retry(stop_max_delay=3000, wait_fixed=500)
-def rmtree(dir, ignore_errors=False):
-    shutil.rmtree(dir, ignore_errors=ignore_errors,
-                  onerror=rmtree_errorhandler)
+def rmtree(dir_, ignore_errors=False):
+    shutil.rmtree(
+        dir_, ignore_errors=ignore_errors, onerror=rmtree_errorhandler
+    )
 
 
 def rmtree_errorhandler(func, path, exc_info):
@@ -211,8 +213,10 @@ def read_chunks(file, size=io.DEFAULT_BUFFER_SIZE):
 
 def split_leading_dir(path):
     path = path.lstrip('/').lstrip('\\')
-    if '/' in path and (('\\' in path and path.find('/') < path.find('\\')) or
-                        '\\' not in path):
+    split_by_forward_slash = (
+        ('\\' in path and path.find('/') < path.find('\\')) or '\\' not in path
+    )
+    if '/' in path and split_by_forward_slash:
         return path.split('/', 1)
     elif '\\' in path:
         return path.split('\\', 1)
@@ -310,9 +314,9 @@ def dist_in_site_packages(dist):
     Return True if given Distribution is installed in
     sysconfig.get_python_lib().
     """
-    return normalize_path(
-        dist_location(dist)
-    ).startswith(normalize_path(site_packages))
+    return normalize_path(dist_location(dist)).startswith(
+        normalize_path(site_packages)
+    )
 
 
 def dist_is_editable(dist):
@@ -590,35 +594,48 @@ def untar_file(filename, location):
 
 def unpack_file(filename, location, content_type, link):
     filename = os.path.realpath(filename)
-    if (content_type == 'application/zip' or
-            filename.lower().endswith(ZIP_EXTENSIONS) or
-            zipfile.is_zipfile(filename)):
-        unzip_file(
-            filename,
-            location,
-            flatten=not filename.endswith('.whl')
+
+    is_zip_file = (
+        content_type == 'application/zip' or
+        filename.lower().endswith(ZIP_EXTENSIONS) or
+        zipfile.is_zipfile(filename)
+    )
+    if is_zip_file:
+        unzip_file(filename, location, flatten=not filename.endswith('.whl'))
+        return
+
+    is_tarball = (
+        content_type == 'application/x-gzip' or
+        tarfile.is_tarfile(filename) or
+        filename.lower().endswith(
+            TAR_EXTENSIONS + BZ2_EXTENSIONS + XZ_EXTENSIONS
         )
-    elif (content_type == 'application/x-gzip' or
-            tarfile.is_tarfile(filename) or
-            filename.lower().endswith(
-                TAR_EXTENSIONS + BZ2_EXTENSIONS + XZ_EXTENSIONS)):
+    )
+    if is_tarball:
         untar_file(filename, location)
-    elif (content_type and content_type.startswith('text/html') and
-            is_svn_page(file_contents(filename))):
+        return
+
+    is_svn_html_page = (
+        content_type and
+        content_type.startswith('text/html') and
+        is_svn_page(file_contents(filename))
+    )
+    if is_svn_html_page:
         # We don't really care about this
         from pip.vcs.subversion import Subversion
         Subversion('svn+' + link.url).unpack(location)
-    else:
-        # FIXME: handle?
-        # FIXME: magic signatures?
-        logger.critical(
-            'Cannot unpack file %s (downloaded from %s, content-type: %s); '
-            'cannot detect archive format',
-            filename, location, content_type,
-        )
-        raise InstallationError(
-            'Cannot determine archive format of %s' % location
-        )
+        return
+
+    # FIXME: handle?
+    # FIXME: magic signatures?
+    logger.critical(
+        'Cannot unpack file %s (downloaded from %s, content-type: %s); '
+        'cannot detect archive format',
+        filename, location, content_type,
+    )
+    raise InstallationError(
+        'Cannot determine archive format of %s' % location
+    )
 
 
 def call_subprocess(cmd, show_stdout=True, cwd=None,
@@ -664,7 +681,8 @@ def call_subprocess(cmd, show_stdout=True, cwd=None,
     try:
         proc = subprocess.Popen(
             cmd, stderr=subprocess.STDOUT, stdin=None, stdout=stdout,
-            cwd=cwd, env=env)
+            cwd=cwd, env=env
+        )
     except Exception as exc:
         logger.critical(
             "Error %s while executing command %s", exc, command_desc,
@@ -697,8 +715,11 @@ def call_subprocess(cmd, show_stdout=True, cwd=None,
             spinner.finish("done")
     if proc.returncode:
         if on_returncode == 'raise':
-            if (logger.getEffectiveLevel() > std_logging.DEBUG and
-                    not show_stdout):
+            should_show_output = (
+                logger.getEffectiveLevel() > std_logging.DEBUG and
+                not show_stdout
+            )
+            if should_show_output:
                 logger.info(
                     'Complete output from command %s:', command_desc,
                 )
diff --git a/pip/utils/outdated.py b/pip/utils/outdated.py
index 517d3bc9a1c..6066a0174d4 100644
--- a/pip/utils/outdated.py
+++ b/pip/utils/outdated.py
@@ -142,10 +142,13 @@ def pip_version_check(session, options):
         remote_version = packaging_version.parse(pypi_version)
 
         # Determine if our pypi_version is older
-        if (pip_version < remote_version and
-                pip_version.base_version != remote_version.base_version):
-            # Advise "python -m pip" on Windows to avoid issues
-            # with overwriting pip.exe.
+        newer_version_available = (
+            pip_version < remote_version and
+            pip_version.base_version != remote_version.base_version
+        )
+        if newer_version_available:
+            # Advise "python -m pip" on Windows to avoid issues with
+            # overwriting pip.exe.
             if WINDOWS:
                 pip_cmd = "python -m pip"
             else:
diff --git a/pip/utils/packaging.py b/pip/utils/packaging.py
index e789d45e61e..d8a27b42b50 100644
--- a/pip/utils/packaging.py
+++ b/pip/utils/packaging.py
@@ -48,16 +48,16 @@ def check_dist_requires_python(dist):
     requires_python = pkg_info_dict.get('Requires-Python')
     try:
         if not check_requires_python(requires_python):
+            version_str = '.'.join(map(str, sys.version_info[:3]))
             raise exceptions.UnsupportedPythonVersion(
-                "%s requires Python '%s' but the running Python is %s" % (
-                    dist.project_name,
-                    requires_python,
-                    '.'.join(map(str, sys.version_info[:3])),)
+                "%s requires Python '%s' but the running Python is %s"
+                % (dist.project_name, requires_python, version_str)
             )
     except specifiers.InvalidSpecifier as e:
         logger.warning(
-            "Package %s has an invalid Requires-Python entry %s - %s" % (
-                dist.project_name, requires_python, e))
+            "Package %s has an invalid Requires-Python entry %s - %s"
+            % (dist.project_name, requires_python, e)
+        )
         return
 
 
diff --git a/pip/utils/temp_dir.py b/pip/utils/temp_dir.py
index d3307d51650..6c9f28ef622 100644
--- a/pip/utils/temp_dir.py
+++ b/pip/utils/temp_dir.py
@@ -30,7 +30,7 @@ class TempDirectory(object):
             Deletes the temporary directory and sets path attribute to None
 
     When used as a context manager, a temporary directory is created on
-    entering the context and, if the delete attribute is True, on exiting the
+    entering the context and if the delete attribute is True, on exiting the
     context the created directory is deleted.
     """
 
diff --git a/pip/vcs/__init__.py b/pip/vcs/__init__.py
index 204155a8575..58c215a434c 100644
--- a/pip/vcs/__init__.py
+++ b/pip/vcs/__init__.py
@@ -74,8 +74,9 @@ def get_backend_name(self, location):
         """
         for vc_type in self._registry.values():
             if vc_type.controls_location(location):
-                logger.debug('Determine that %s uses VCS: %s',
-                             location, vc_type.name)
+                logger.debug(
+                    'Determine that %s uses VCS: %s', location, vc_type.name
+                )
                 return vc_type.name
         return None
 
@@ -207,55 +208,47 @@ def check_destination(self, dest, url, rev_options, rev_display):
                 if self.compare_urls(existing_url, url):
                     logger.debug(
                         '%s in %s exists, and has correct URL (%s)',
-                        self.repo_name.title(),
-                        display_path(dest),
-                        url,
+                        self.repo_name.title(), display_path(dest), url,
                     )
                     if not self.check_version(dest, rev_options):
                         logger.info(
                             'Updating %s %s%s',
-                            display_path(dest),
-                            self.repo_name,
-                            rev_display,
+                            display_path(dest), self.repo_name, rev_display,
                         )
                         self.update(dest, rev_options)
                     else:
                         logger.info(
-                            'Skipping because already up-to-date.')
+                            'Skipping because already up-to-date.'
+                        )
                 else:
                     logger.warning(
                         '%s %s in %s exists with URL %s',
-                        self.name,
-                        self.repo_name,
-                        display_path(dest),
+                        self.name, self.repo_name, display_path(dest),
                         existing_url,
                     )
-                    prompt = ('(s)witch, (i)gnore, (w)ipe, (b)ackup ',
-                              ('s', 'i', 'w', 'b'))
+                    prompt = (
+                        '(s)witch, (i)gnore, (w)ipe, (b)ackup ',
+                        ('s', 'i', 'w', 'b')
+                    )
             else:
                 logger.warning(
                     'Directory %s already exists, and is not a %s %s.',
-                    dest,
-                    self.name,
-                    self.repo_name,
+                    dest, self.name, self.repo_name,
                 )
                 prompt = ('(i)gnore, (w)ipe, (b)ackup ', ('i', 'w', 'b'))
         if prompt:
             logger.warning(
                 'The plan is to install the %s repository %s',
-                self.name,
-                url,
+                self.name, url,
             )
-            response = ask_path_exists('What to do?  %s' % prompt[0],
-                                       prompt[1])
 
+            response = ask_path_exists(
+                'What to do?  %s' % prompt[0], prompt[1]
+            )
             if response == 's':
                 logger.info(
                     'Switching %s %s to %s%s',
-                    self.repo_name,
-                    display_path(dest),
-                    url,
-                    rev_display,
+                    self.repo_name, display_path(dest), url, rev_display,
                 )
                 self.switch(dest, url, rev_options)
             elif response == 'i':
@@ -319,18 +312,19 @@ def run_command(self, cmd, show_stdout=True, cwd=None,
         """
         cmd = [self.name] + cmd
         try:
-            return call_subprocess(cmd, show_stdout, cwd,
-                                   on_returncode,
-                                   command_desc, extra_environ,
-                                   spinner)
+            return call_subprocess(
+                cmd, show_stdout, cwd, on_returncode, command_desc,
+                extra_environ, spinner
+            )
         except OSError as e:
             # errno.ENOENT = no such file or directory
             # In other words, the VCS executable isn't available
             if e.errno == errno.ENOENT:
                 raise BadCommand(
                     'Cannot find command %r - do you have '
-                    '%r installed and in your '
-                    'PATH?' % (self.name, self.name))
+                    '%r installed and in your PATH?'
+                    % (self.name, self.name)
+                )
             else:
                 raise  # re-raise exception if a different error occurred
 
@@ -341,8 +335,9 @@ def controls_location(cls, location):
         It is meant to be overridden to implement smarter detection
         mechanisms for specific vcs.
         """
-        logger.debug('Checking in %s for %s (%s)...',
-                     location, cls.dirname, cls.name)
+        logger.debug(
+            'Checking in %s for %s (%s)...', location, cls.dirname, cls.name
+        )
         path = os.path.join(location, cls.dirname)
         return os.path.exists(path)
 
@@ -351,14 +346,12 @@ def get_src_requirement(dist, location):
     version_control = vcs.get_backend_from_location(location)
     if version_control:
         try:
-            return version_control().get_src_requirement(dist,
-                                                         location)
+            return version_control().get_src_requirement(dist, location)
         except BadCommand:
             logger.warning(
                 'cannot determine version of editable source in %s '
                 '(%s command not found in path)',
-                location,
-                version_control.name,
+                location, version_control.name,
             )
             return dist.as_requirement()
     logger.warning(
diff --git a/pip/vcs/bazaar.py b/pip/vcs/bazaar.py
index 8a53d741513..e5072591c54 100644
--- a/pip/vcs/bazaar.py
+++ b/pip/vcs/bazaar.py
@@ -79,8 +79,7 @@ def get_url(self, location):
         urls = self.run_command(['info'], show_stdout=False, cwd=location)
         for line in urls.splitlines():
             line = line.strip()
-            for x in ('checkout of branch: ',
-                      'parent branch: '):
+            for x in ('checkout of branch: ', 'parent branch: '):
                 if line.startswith(x):
                     repo = line.split(x)[1]
                     if self._is_local_repository(repo):
@@ -89,8 +88,7 @@ def get_url(self, location):
         return None
 
     def get_revision(self, location):
-        revision = self.run_command(
-            ['revno'], show_stdout=False, cwd=location)
+        revision = self.run_command(['revno'], show_stdout=False, cwd=location)
         return revision.splitlines()[-1]
 
     def get_src_requirement(self, dist, location):
diff --git a/pip/vcs/git.py b/pip/vcs/git.py
index c1d02ad766e..2ef8fb11fac 100644
--- a/pip/vcs/git.py
+++ b/pip/vcs/git.py
@@ -145,12 +145,10 @@ def obtain(self, dest):
                 # Only do a checkout if rev_options differs from HEAD
                 if not self.check_version(dest, rev_options):
                     self.run_command(
-                        ['fetch', '-q', url] + rev_options,
-                        cwd=dest,
+                        ['fetch', '-q', url] + rev_options, cwd=dest,
                     )
                     self.run_command(
-                        ['checkout', '-q', 'FETCH_HEAD'],
-                        cwd=dest,
+                        ['checkout', '-q', 'FETCH_HEAD'], cwd=dest,
                     )
 
             #: repo may contain submodules
@@ -160,7 +158,8 @@ def get_url(self, location):
         """Return URL of the first remote encountered."""
         remotes = self.run_command(
             ['config', '--get-regexp', r'remote\..*\.url'],
-            show_stdout=False, cwd=location)
+            show_stdout=False, cwd=location
+        )
         remotes = remotes.splitlines()
         found_remote = remotes[0]
         for remote in remotes:
@@ -172,13 +171,15 @@ def get_url(self, location):
 
     def get_revision(self, location):
         current_rev = self.run_command(
-            ['rev-parse', 'HEAD'], show_stdout=False, cwd=location)
+            ['rev-parse', 'HEAD'], show_stdout=False, cwd=location
+        )
         return current_rev.strip()
 
     def get_full_refs(self, location):
         """Yields tuples of (commit, ref) for branches and tags"""
-        output = self.run_command(['show-ref'],
-                                  show_stdout=False, cwd=location)
+        output = self.run_command(
+            ['show-ref'], show_stdout=False, cwd=location
+        )
         for line in output.strip().splitlines():
             commit, ref = line.split(' ', 1)
             yield commit.strip(), ref.strip()
@@ -222,8 +223,9 @@ def get_short_refs(self, location):
     def _get_subdirectory(self, location):
         """Return the relative path of setup.py to the git repo root."""
         # find the repo root
-        git_dir = self.run_command(['rev-parse', '--git-dir'],
-                                   show_stdout=False, cwd=location).strip()
+        git_dir = self.run_command(
+            ['rev-parse', '--git-dir'], show_stdout=False, cwd=location
+        ).strip()
         if not os.path.isabs(git_dir):
             git_dir = os.path.join(location, git_dir)
         root_dir = os.path.join(git_dir, '..')
@@ -290,14 +292,16 @@ def controls_location(cls, location):
         if super(Git, cls).controls_location(location):
             return True
         try:
-            r = cls().run_command(['rev-parse'],
-                                  cwd=location,
-                                  show_stdout=False,
-                                  on_returncode='ignore')
+            r = cls().run_command(
+                ['rev-parse'], cwd=location, show_stdout=False,
+                on_returncode='ignore'
+            )
             return not r
         except BadCommand:
-            logger.debug("could not determine if %s is under git control "
-                         "because git is not available", location)
+            logger.debug(
+                "Could not determine if %s is under git control "
+                "because git is not available", location
+            )
             return False
 
 
diff --git a/pip/vcs/mercurial.py b/pip/vcs/mercurial.py
index c9226d6a3ec..40f9579a3ec 100644
--- a/pip/vcs/mercurial.py
+++ b/pip/vcs/mercurial.py
@@ -68,7 +68,8 @@ def obtain(self, dest):
     def get_url(self, location):
         url = self.run_command(
             ['showconfig', 'paths.default'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False, cwd=location
+        ).strip()
         if self._is_local_repository(url):
             url = path_to_url(url)
         return url.strip()
@@ -76,13 +77,15 @@ def get_url(self, location):
     def get_revision(self, location):
         current_revision = self.run_command(
             ['parents', '--template={rev}'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False, cwd=location
+        ).strip()
         return current_revision
 
     def get_revision_hash(self, location):
         current_rev_hash = self.run_command(
             ['parents', '--template={node}'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False, cwd=location
+        ).strip()
         return current_rev_hash
 
     def get_src_requirement(self, dist, location):
diff --git a/pip/vcs/subversion.py b/pip/vcs/subversion.py
index 77b66c91e09..213e864716f 100644
--- a/pip/vcs/subversion.py
+++ b/pip/vcs/subversion.py
@@ -33,9 +33,7 @@ def get_info(self, location):
         assert not location.rstrip('/').endswith(self.dirname), \
             'Bad directory: %s' % location
         output = self.run_command(
-            ['info', location],
-            show_stdout=False,
-            extra_environ={'LANG': 'C'},
+            ['info', location], show_stdout=False, extra_environ={'LANG': 'C'}
         )
         match = _svn_url_re.search(output)
         if not match:
@@ -69,7 +67,8 @@ def export(self, location):
                 rmtree(location)
             self.run_command(
                 ['export'] + rev_options + [url, location],
-                show_stdout=False)
+                show_stdout=False
+            )
 
     def switch(self, dest, url, rev_options):
         self.run_command(['switch'] + rev_options + [url, dest])
@@ -172,9 +171,7 @@ def _get_svn_url_rev(self, location):
         else:  # subversion >= 1.7 does not have the 'entries' file
             data = ''
 
-        if (data.startswith('8') or
-                data.startswith('9') or
-                data.startswith('10')):
+        if data.startswith(('8', '9', '10')):
             data = list(map(str.splitlines, data.split('\n\x0c\n')))
             del data[0][0]  # get rid of the '8'
             url = data[0][3]
diff --git a/pip/wheel.py b/pip/wheel.py
index 31cceed19ef..de7d11deb0b 100644
--- a/pip/wheel.py
+++ b/pip/wheel.py
@@ -52,9 +52,8 @@ def rehash(path, algo='sha256', blocksize=1 << 20):
         for block in read_chunks(f, size=blocksize):
             length += len(block)
             h.update(block)
-    digest = 'sha256=' + urlsafe_b64encode(
-        h.digest()
-    ).decode('latin1').rstrip('=')
+    digest = 'sha256='
+    digest += urlsafe_b64encode(h.digest()).decode('latin1').rstrip('=')
     return (digest, length)
 
 
@@ -86,8 +85,9 @@ def fix_script(path):
         return True
 
 
-dist_info_re = re.compile(r"""^(?P<namever>(?P<name>.+?)(-(?P<ver>.+?))?)
-                                \.dist-info$""", re.VERBOSE)
+dist_info_re = re.compile(
+    r"^(?P<namever>(?P<name>.+?)(-(?P<ver>.+?))?)\.dist-info$", re.VERBOSE
+)
 
 
 def root_is_purelib(name, wheeldir):
@@ -623,12 +623,17 @@ def _install_build_reqs(self, reqs, prefix):
         # we don't recurse trying to build a self-hosting build system.
         finder = copy.copy(self.finder)
         finder.format_control = FormatControl(set(), set())
-        urls = [finder.find_requirement(InstallRequirement.from_line(r),
-                                        upgrade=False).url
-                for r in reqs]
+        urls = [
+            finder.find_requirement(
+                InstallRequirement.from_line(r), upgrade=False
+            ).url
+            for r in reqs
+        ]
 
-        args = [sys.executable, '-m', 'pip', 'install', '--ignore-installed',
-                '--prefix', prefix] + list(urls)
+        args = [
+            sys.executable, '-m', 'pip', 'install', '--ignore-installed',
+            '--prefix', prefix
+        ] + list(urls)
         with open_spinner("Installing build dependencies") as spinner:
             call_subprocess(args, show_stdout=False, spinner=spinner)
 
@@ -642,19 +647,22 @@ def _build_one(self, req, output_dir, python_tag=None):
             logger.warning(
                 "This version of pip does not implement PEP 516, so "
                 "it cannot build a wheel without setuptools. You may need to "
-                "upgrade to a newer version of pip.")
+                "upgrade to a newer version of pip."
+            )
         # Install build deps into temporary directory (PEP 518)
         with BuildEnvironment(self.no_clean) as prefix:
             self._install_build_reqs(build_reqs, prefix)
-            return self._build_one_inside_env(req, output_dir,
-                                              python_tag=python_tag,
-                                              isolate=True)
+            return self._build_one_inside_env(
+                req, output_dir, python_tag=python_tag, isolate=True
+            )
 
     def _build_one_inside_env(self, req, output_dir, python_tag=None,
                               isolate=False):
         with TempDirectory(kind="wheel") as temp_dir:
-            if self.__build_one(req, temp_dir.path, python_tag=python_tag,
-                                isolate=isolate):
+            built_it = self.__build_one(
+                req, temp_dir.path, python_tag=python_tag, isolate=isolate
+            )
+            if built_it:
                 try:
                     wheel_name = os.listdir(temp_dir.path)[0]
                     wheel_path = os.path.join(output_dir, wheel_name)
@@ -698,9 +706,10 @@ def __build_one(self, req, tempd, python_tag=None, isolate=False):
                 env['PYTHONNOUSERSITE'] = '1'
 
             try:
-                call_subprocess(wheel_args, cwd=req.setup_py_dir,
-                                extra_environ=env,
-                                show_stdout=False, spinner=spinner)
+                call_subprocess(
+                    wheel_args, cwd=req.setup_py_dir, extra_environ=env,
+                    show_stdout=False, spinner=spinner
+                )
                 return True
             except:
                 spinner.finish("error")
@@ -740,7 +749,8 @@ def build(self, session, autobuilding=False):
             if req.is_wheel:
                 if not autobuilding:
                     logger.info(
-                        'Skipping %s, due to already being wheel.', req.name)
+                        'Skipping %s, due to already being wheel.', req.name
+                    )
             elif autobuilding and req.editable:
                 pass
             elif autobuilding and req.link and not req.link.is_artifact:
@@ -760,7 +770,8 @@ def build(self, session, autobuilding=False):
                             canonicalize_name(req.name)):
                         logger.info(
                             "Skipping bdist_wheel for %s, due to binaries "
-                            "being disabled for it.", req.name)
+                            "being disabled for it.", req.name
+                        )
                         continue
                 buildset.append(req)
 
@@ -782,8 +793,9 @@ def build(self, session, autobuilding=False):
                     try:
                         ensure_dir(output_dir)
                     except OSError as e:
-                        logger.warning("Building wheel for %s failed: %s",
-                                       req.name, e)
+                        logger.warning(
+                            "Building wheel for %s failed: %s", req.name, e
+                        )
                         build_failure.append(req)
                         continue
                 else:
@@ -795,30 +807,36 @@ def build(self, session, autobuilding=False):
                 if wheel_file:
                     build_success.append(req)
                     if autobuilding:
-                        # XXX: This is mildly duplicative with prepare_files,
+                        # XXX: This is mildly duplicative with Resolver,
                         # but not close enough to pull out to a single common
                         # method.
                         # The code below assumes temporary source dirs -
                         # prevent it doing bad things.
-                        if req.source_dir and not os.path.exists(os.path.join(
-                                req.source_dir, PIP_DELETE_MARKER_FILENAME)):
+                        bad_src_dir = (
+                            req.source_dir and
+                            not os.path.exists(os.path.join(
+                                req.source_dir, PIP_DELETE_MARKER_FILENAME
+                            ))
+                        )
+                        if bad_src_dir:
                             raise AssertionError(
-                                "bad source dir - missing marker")
+                                "bad source dir - missing marker"
+                            )
                         # Delete the source we built the wheel from
                         req.remove_temporary_source()
                         # set the build directory again - name is known from
-                        # the work prepare_files did.
+                        # the work Resolver did.
                         req.source_dir = req.build_location(
                             self.preparer.build_dir
                         )
                         # Update the link for this.
-                        req.link = pip.index.Link(
-                            path_to_url(wheel_file))
+                        req.link = pip.index.Link(path_to_url(wheel_file))
                         assert req.link.is_wheel
                         # extract the wheel into the dir
                         unpack_url(
                             req.link, req.source_dir, None, False,
-                            session=session)
+                            session=session
+                        )
                 else:
                     build_failure.append(req)