py 2.7 mentions removed from README and setup.py (#2852)

* 2.7 mentions removed from README and setup.py

* py27 -> py37 in CONTRIBUTING.rst

CONTRIBUTING.rst

@@ -22,10 +22,10 @@ You will need a ``tox --version`` of at least 2.0.
     # These commands are pretty fast and will tell if you've
     # broken something major:
     tox -e flake8
-    tox -e py27-core
+    tox -e py37-core
 
     # You can also test particular files for even faster iterations
-    tox -e py27-core test/rpc_test.py
+    tox -e py37-core test/rpc_test.py
 
     # The visualiser tests require phantomjs to be installed on your path
     tox -e visualiser
@@ -34,7 +34,7 @@ You will need a ``tox --version`` of at least 2.0.
     tox -e py33-cdh
     tox -e py34-hdp
 
-Where ``flake8`` is the lint checking, ``py27`` is obviously Python 2.7.
+Where ``flake8`` is the lint checking, ``py37`` is obviously Python 3.7.
 ``core`` are tests that do not require external components and ``cdh`` and
 ``hdp`` are two different hadoop distributions. For most local development it's
 usually enough to run the lint checking and a python version for ``core``

README.rst

@@ -17,7 +17,7 @@
 .. image:: https://img.shields.io/pypi/l/luigi.svg?style=flat
    :target: https://pypi.python.org/pypi/luigi
 
-Luigi is a Python (2.7, 3.6, 3.7 tested) package that helps you build complex
+Luigi is a Python (3.6, 3.7 tested) package that helps you build complex
 pipelines of batch jobs. It handles dependency resolution, workflow management,
 visualization, handling failures, command line integration, and much more.
 

setup.py

@@ -47,9 +47,8 @@ def get_static_files(path):
     install_requires.append('python-daemon')
 
 # Tornado >=5 requires updated ssl module so we only allow it for recent enough
-# versions of python (3.4+ and 2.7.9+).
-if sys.version_info[:2] >= (3, 4) or (sys.version_info[:2] == (2, 7) and
-                                      sys.version_info[2] >= 9):
+# versions of python (3.4+).
+if sys.version_info[:2] >= (3, 4):
     install_requires.append('tornado>=4.0,<6')
 else:
     install_requires.append('tornado>=4.0,<5')
@@ -112,7 +111,6 @@ def get_static_files(path):
         'Intended Audience :: Developers',
         'Intended Audience :: System Administrators',
         'License :: OSI Approved :: Apache Software License',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',