No module named virtualenv when running under PYTHONPATH

[jaraco]

Easiest way to reproduce is with pip-run:

$ cat > test.py
__requires__ = ['pytest-virtualenv']


def test_run(virtualenv):
    pass
$ pip-run -- -m pytest test.py
Collecting pytest-virtualenv
  Using cached pytest_virtualenv-1.7.0-py2.py3-none-any.whl (9.5 kB)
Collecting pytest-fixture-config
  Using cached pytest_fixture_config-1.7.0-py2.py3-none-any.whl (6.5 kB)
Collecting virtualenv
  Using cached virtualenv-20.0.30-py2.py3-none-any.whl (7.1 MB)
Collecting pytest
  Using cached pytest-6.0.1-py3-none-any.whl (270 kB)
Collecting pytest-shutil
  Using cached pytest_shutil-1.7.0-py2.py3-none-any.whl (15 kB)
Collecting appdirs<2,>=1.4.3
  Using cached appdirs-1.4.4-py2.py3-none-any.whl (9.6 kB)
Collecting filelock<4,>=3.0.0
  Using cached filelock-3.0.12-py3-none-any.whl (7.6 kB)
Collecting six<2,>=1.9.0
  Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Collecting distlib<1,>=0.3.1
  Using cached distlib-0.3.1-py2.py3-none-any.whl (335 kB)
Collecting iniconfig
  Using cached iniconfig-1.0.1-py3-none-any.whl (4.2 kB)
Collecting toml
  Using cached toml-0.10.1-py2.py3-none-any.whl (19 kB)
Collecting pluggy<1.0,>=0.12
  Using cached pluggy-0.13.1-py2.py3-none-any.whl (18 kB)
Collecting packaging
  Using cached packaging-20.4-py2.py3-none-any.whl (37 kB)
Collecting py>=1.8.2
  Using cached py-1.9.0-py2.py3-none-any.whl (99 kB)
Collecting attrs>=17.4.0
  Using cached attrs-19.3.0-py2.py3-none-any.whl (39 kB)
Collecting more-itertools>=4.0.0
  Using cached more_itertools-8.4.0-py3-none-any.whl (43 kB)
Collecting execnet
  Using cached execnet-1.7.1-py2.py3-none-any.whl (39 kB)
Collecting path.py
  Using cached path.py-12.5.0-py3-none-any.whl (2.3 kB)
Processing /Users/jaraco/Library/Caches/pip/wheels/7c/06/54/bc84598ba1daf8f970247f550b175aaaee85f68b4b0c5ab2c6/termcolor-1.1.0-cp38-none-any.whl
Collecting mock
  Using cached mock-4.0.2-py3-none-any.whl (28 kB)
Collecting contextlib2
  Using cached contextlib2-0.6.0.post1-py2.py3-none-any.whl (9.8 kB)
Collecting pyparsing>=2.0.2
  Using cached pyparsing-2.4.7-py2.py3-none-any.whl (67 kB)
Collecting apipkg>=1.4
  Using cached apipkg-1.5-py2.py3-none-any.whl (4.9 kB)
Collecting path
  Using cached path-15.0.0-py3-none-any.whl (21 kB)
Installing collected packages: iniconfig, toml, pluggy, pyparsing, six, packaging, py, attrs, more-itertools, pytest, pytest-fixture-config, appdirs, filelock, distlib, virtualenv, apipkg, execnet, path, path.py, termcolor, mock, contextlib2, pytest-shutil, pytest-virtualenv
Successfully installed apipkg-1.5 appdirs-1.4.4 attrs-19.3.0 contextlib2-0.6.0.post1 distlib-0.3.1 execnet-1.7.1 filelock-3.0.12 iniconfig-1.0.1 mock-4.0.2 more-itertools-8.4.0 packaging-20.4 path-15.0.0 path.py-12.5.0 pluggy-0.13.1 py-1.9.0 pyparsing-2.4.7 pytest-6.0.1 pytest-fixture-config-1.7.0 pytest-shutil-1.7.0 pytest-virtualenv-1.7.0 six-1.15.0 termcolor-1.1.0 toml-0.10.1 virtualenv-20.0.30
WARNING: You are using pip version 20.2; however, version 20.2.1 is available.
You should consider upgrading via the '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8 -m pip install --upgrade pip' command.
=========================================================== test session starts ============================================================
platform darwin -- Python 3.8.5, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /Users/jaraco/draft
plugins: shutil-1.7.0, virtualenv-1.7.0, black-multipy-1.0.0, black-0.3.8, flake8-1.0.5, checkdocs-1.2.3, cov-2.8.1
collected 1 item                                                                                                                           

test.py E                                                                                                                            [100%]

================================================================== ERRORS ==================================================================
________________________________________________________ ERROR at setup of test_run ________________________________________________________

args = (), kwargs = {}, var = 'virtualenv_executable', gen = <generator object virtualenv at 0x7f8277243040>

    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        for var in vars_:
            if not getattr(cfg, var):
                pytest.skip('config variable {0} missing, skipping test'.format(var))
        gen = f(*args, **kwargs)
>       yield next(gen)

/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-hirmpjlp/pytest_fixture_config.py:47: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-hirmpjlp/pytest_virtualenv.py:50: in virtualenv
    venv = VirtualEnv()
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-hirmpjlp/pytest_virtualenv.py:143: in __init__
    self.run(cmd)
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-hirmpjlp/pytest_virtualenv.py:151: in run
    return super(VirtualEnv, self).run(args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <pytest_virtualenv.VirtualEnv object at 0x7f82770fbee0>
cmd = ['/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '-m', 'virtualenv', '-p', '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmp7n3bqfab/.env']
capture = False, check_rc = True, cd = Path('/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmp7n3bqfab'), shell = False
kwargs = {'env': {'BASH_COMPLETIONS': '/usr/local/share/bash-completion/bash_completion:/usr/local/etc/bash_completion', 'BASH_COMPLETION_COMPAT_DIR': '/usr/local/etc/bash_completion.d', 'COLORTERM': 'truecolor', 'EDITOR': 'subl --wait', ...}}
p = <subprocess.Popen object at 0x7f82770efee0>, out = None, _ = None
err = CalledProcessError(1, ['/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '-m', 'virtualenv', '-p', '/...rks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmp7n3bqfab/.env'])

    def run(self, cmd, capture=False, check_rc=True, cd=None, shell=False, **kwargs):
        """
        Run a command relative to a given directory, defaulting to the workspace root
    
        Parameters
        ----------
        cmd : `str` or `list`
            Command string or list. Commands given as a string will be run in a subshell.
        capture : `bool`
            Capture and return output
        check_rc : `bool`
            Assert return code is zero
        cd : `str`
            Path to chdir to, defaults to workspace root
        """
        if isinstance(cmd, string_types):
            shell = True
        else:
            # Some of the command components might be path objects or numbers
            cmd = [str(i) for i in cmd]
    
        if not cd:
            cd = self.workspace
    
        with cmdline.chdir(cd):
            log.debug("run: {0}".format(cmd))
            if capture:
                p = subprocess.Popen(cmd, shell=shell, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kwargs)
            else:
                p = subprocess.Popen(cmd, shell=shell, **kwargs)
            (out, _) = p.communicate()
    
            if out is not None and not isinstance(out, string_types):
                out = out.decode('utf-8')
    
            if self.debug and capture:
                log.debug("Stdout/stderr:")
                log.debug(out)
    
            if check_rc and p.returncode != 0:
                err = subprocess.CalledProcessError(p.returncode, cmd)
                err.output = out
                if capture and not self.debug:
                    log.error("Stdout/stderr:")
                    log.error(out)
>               raise err
E               subprocess.CalledProcessError: Command '['/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '-m', 'virtualenv', '-p', '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmp7n3bqfab/.env']' returned non-zero exit status 1.

/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-hirmpjlp/pytest_shutil/workspace.py:132: CalledProcessError
---------------------------------------------------------- Captured stderr setup -----------------------------------------------------------
/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8: No module named virtualenv
========================================================= short test summary info ==========================================================
ERROR test.py::test_run - subprocess.CalledProcessError: Command '['/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '-m...
============================================================= 1 error in 0.11s =============================================================

To reproduce without pip-run:

$ cat > test.py
def test_run(virtualenv):
    pass
$ pip install -t libs pytest-virtualenv
Collecting pytest-virtualenv
  Using cached pytest_virtualenv-1.7.0-py2.py3-none-any.whl (9.5 kB)
Collecting pytest-fixture-config
  Using cached pytest_fixture_config-1.7.0-py2.py3-none-any.whl (6.5 kB)
Collecting virtualenv
  Using cached virtualenv-20.0.30-py2.py3-none-any.whl (7.1 MB)
Collecting pytest
  Using cached pytest-6.0.1-py3-none-any.whl (270 kB)
Collecting pytest-shutil
  Using cached pytest_shutil-1.7.0-py2.py3-none-any.whl (15 kB)
Collecting distlib<1,>=0.3.1
  Using cached distlib-0.3.1-py2.py3-none-any.whl (335 kB)
Collecting six<2,>=1.9.0
  Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Collecting appdirs<2,>=1.4.3
  Using cached appdirs-1.4.4-py2.py3-none-any.whl (9.6 kB)
Collecting filelock<4,>=3.0.0
  Using cached filelock-3.0.12-py3-none-any.whl (7.6 kB)
Collecting importlib-metadata<2,>=0.12; python_version < "3.8"
  Using cached importlib_metadata-1.7.0-py2.py3-none-any.whl (31 kB)
Collecting iniconfig
  Using cached iniconfig-1.0.1-py3-none-any.whl (4.2 kB)
Collecting attrs>=17.4.0
  Using cached attrs-19.3.0-py2.py3-none-any.whl (39 kB)
Collecting more-itertools>=4.0.0
  Using cached more_itertools-8.4.0-py3-none-any.whl (43 kB)
Collecting py>=1.8.2
  Using cached py-1.9.0-py2.py3-none-any.whl (99 kB)
Collecting pluggy<1.0,>=0.12
  Using cached pluggy-0.13.1-py2.py3-none-any.whl (18 kB)
Collecting toml
  Using cached toml-0.10.1-py2.py3-none-any.whl (19 kB)
Collecting packaging
  Using cached packaging-20.4-py2.py3-none-any.whl (37 kB)
Collecting mock
  Using cached mock-4.0.2-py3-none-any.whl (28 kB)
Collecting path.py
  Using cached path.py-12.5.0-py3-none-any.whl (2.3 kB)
Processing /Users/jaraco/Library/Caches/pip/wheels/7c/06/54/bc84598ba1daf8f970247f550b175aaaee85f68b4b0c5ab2c6/termcolor-1.1.0-cp37-none-any.whl
Collecting contextlib2
  Using cached contextlib2-0.6.0.post1-py2.py3-none-any.whl (9.8 kB)
Collecting execnet
  Using cached execnet-1.7.1-py2.py3-none-any.whl (39 kB)
Collecting zipp>=0.5
  Using cached zipp-3.1.0-py3-none-any.whl (4.9 kB)
Collecting pyparsing>=2.0.2
  Using cached pyparsing-2.4.7-py2.py3-none-any.whl (67 kB)
Collecting path
  Using cached path-15.0.0-py3-none-any.whl (21 kB)
Collecting apipkg>=1.4
  Using cached apipkg-1.5-py2.py3-none-any.whl (4.9 kB)
Installing collected packages: iniconfig, attrs, more-itertools, py, zipp, importlib-metadata, pluggy, toml, pyparsing, six, packaging, pytest, pytest-fixture-config, distlib, appdirs, filelock, virtualenv, mock, path, path.py, termcolor, contextlib2, apipkg, execnet, pytest-shutil, pytest-virtualenv
Successfully installed apipkg-1.5 appdirs-1.4.4 attrs-19.3.0 contextlib2-0.6.0.post1 distlib-0.3.1 execnet-1.7.1 filelock-3.0.12 importlib-metadata-1.7.0 iniconfig-1.0.1 mock-4.0.2 more-itertools-8.4.0 packaging-20.4 path-15.0.0 path.py-12.5.0 pluggy-0.13.1 py-1.9.0 pyparsing-2.4.7 pytest-6.0.1 pytest-fixture-config-1.7.0 pytest-shutil-1.7.0 pytest-virtualenv-1.7.0 six-1.15.0 termcolor-1.1.0 toml-0.10.1 virtualenv-20.0.30 zipp-3.1.0
WARNING: You are using pip version 20.2; however, version 20.2.1 is available.
You should consider upgrading via the '/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 -m pip install --upgrade pip' command.
$ env PYTHONPATH=libs python -m pytest test.py
=========================================================== test session starts ============================================================
platform darwin -- Python 3.8.5, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /Users/jaraco/draft
plugins: shutil-1.7.0, virtualenv-1.7.0, black-multipy-1.0.0, black-0.3.8, flake8-1.0.5, checkdocs-1.2.3, cov-2.8.1
collected 1 item                                                                                                                           

test.py E                                                                                                                            [100%]

================================================================== ERRORS ==================================================================
________________________________________________________ ERROR at setup of test_run ________________________________________________________

args = (), kwargs = {}, var = 'virtualenv_executable', gen = <generator object virtualenv at 0x7f99df948190>

    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        for var in vars_:
            if not getattr(cfg, var):
                pytest.skip('config variable {0} missing, skipping test'.format(var))
        gen = f(*args, **kwargs)
>       yield next(gen)

libs/pytest_fixture_config.py:47: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
libs/pytest_virtualenv.py:50: in virtualenv
    venv = VirtualEnv()
libs/pytest_virtualenv.py:143: in __init__
    self.run(cmd)
libs/pytest_virtualenv.py:151: in run
    return super(VirtualEnv, self).run(args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <pytest_virtualenv.VirtualEnv object at 0x7f99df92c280>
cmd = ['/usr/local/bin/python', '-m', 'virtualenv', '-p', '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmporcm9r1f/.env']
capture = False, check_rc = True, cd = Path('/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmporcm9r1f'), shell = False
kwargs = {'env': {'BASH_COMPLETIONS': '/usr/local/share/bash-completion/bash_completion:/usr/local/etc/bash_completion', 'BASH_COMPLETION_COMPAT_DIR': '/usr/local/etc/bash_completion.d', 'COLORTERM': 'truecolor', 'EDITOR': 'subl --wait', ...}}
p = <subprocess.Popen object at 0x7f99df92ca00>, out = None, _ = None
err = CalledProcessError(1, ['/usr/local/bin/python', '-m', 'virtualenv', '-p', '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmporcm9r1f/.env'])

    def run(self, cmd, capture=False, check_rc=True, cd=None, shell=False, **kwargs):
        """
        Run a command relative to a given directory, defaulting to the workspace root
    
        Parameters
        ----------
        cmd : `str` or `list`
            Command string or list. Commands given as a string will be run in a subshell.
        capture : `bool`
            Capture and return output
        check_rc : `bool`
            Assert return code is zero
        cd : `str`
            Path to chdir to, defaults to workspace root
        """
        if isinstance(cmd, string_types):
            shell = True
        else:
            # Some of the command components might be path objects or numbers
            cmd = [str(i) for i in cmd]
    
        if not cd:
            cd = self.workspace
    
        with cmdline.chdir(cd):
            log.debug("run: {0}".format(cmd))
            if capture:
                p = subprocess.Popen(cmd, shell=shell, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kwargs)
            else:
                p = subprocess.Popen(cmd, shell=shell, **kwargs)
            (out, _) = p.communicate()
    
            if out is not None and not isinstance(out, string_types):
                out = out.decode('utf-8')
    
            if self.debug and capture:
                log.debug("Stdout/stderr:")
                log.debug(out)
    
            if check_rc and p.returncode != 0:
                err = subprocess.CalledProcessError(p.returncode, cmd)
                err.output = out
                if capture and not self.debug:
                    log.error("Stdout/stderr:")
                    log.error(out)
>               raise err
E               subprocess.CalledProcessError: Command '['/usr/local/bin/python', '-m', 'virtualenv', '-p', '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8', '/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/tmporcm9r1f/.env']' returned non-zero exit status 1.

libs/pytest_shutil/workspace.py:132: CalledProcessError
---------------------------------------------------------- Captured stderr setup -----------------------------------------------------------
/usr/local/bin/python: No module named virtualenv
========================================================= short test summary info ==========================================================
ERROR test.py::test_run - subprocess.CalledProcessError: Command '['/usr/local/bin/python', '-m', 'virtualenv', '-p', '/Library/Framework...
============================================================= 1 error in 0.11s =============================================================

I suspect the issue is that pytest-virtualenv is suppressing the PYTHONPATH when executing virtualenv.