multiprocessing broken since 2.7.1 on Windows

[pytestbot]

Originally reported by: Marc Schlaich (BitBucket: schlamar, GitHub: schlamar)

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With pytest 2.7.1, Processes with multiprocessing don't start anymore, I'm seeing this in stdout:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "c:\python27\Lib\multiprocessing\forking.py", line 380, in main
    prepare(preparation_data)
  File "c:\python27\Lib\multiprocessing\forking.py", line 488, in prepare
    assert main_name not in sys.modules, main_name
AssertionError: __main__

This is probably due to this upstream issue with wheels: pypa/pip#1891

Installing pytest not as wheel with pip install --no-use-wheel resolves this issue.

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• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/749

[pytestbot]

Original comment by Floris Bruynooghe (BitBucket: flub, GitHub: flub):

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As you say this appear to be a wheel issue. Is the suggestion we remove the wheel again until the referenced issue gets fixed? Not sure what else we can do really.

[pytestbot]

Original comment by Bruno Oliveira (BitBucket: nicoddemus, GitHub: nicoddemus):

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I guess that would be the correct approach, IMO.

[pytestbot]

Original comment by Marc Schlaich (BitBucket: schlamar, GitHub: schlamar):

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Yes. This is what autopep8 did, too: hhatto/autopep8#193

[pytestbot]

Original comment by Floris Bruynooghe (BitBucket: flub, GitHub: flub):

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Sigh, seems like the poor people wanting wheels never get to have their fun.

Since I've heard issues with deleting files on pypi, are we very sure we want to delete it? we might not be able to add it back. And is it completely safe to remove the wheel file from it.

[pytestbot]

Original comment by Bruno Oliveira (BitBucket: nicoddemus, GitHub: nicoddemus):

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Sigh, seems like the poor people wanting wheels never get to have their fun

Indeed. :(

Since I've heard issues with deleting files on pypi, are we very sure we want to delete it? we might not be able to add it back.

I'm not sure... I think the best policy would be to release a hotfix version of pytest (2.7.2) without wheels, otherwise folks from now on would never be sure if their version was installed using a wheel or not, specially on CI farms and cached virtual envs. sigh

[schlamar]

This is not resolved, there are wheels on 2.8.2 :(

[The-Compiler]

HOWTORELEASE.rst says to build wheels, so that's what I did when doing my first release 😉

Honestly, I personally don't think it's the correct solution to avoid building wheels for pytest.

pypa/pip#1891 mentions running wheel install-scripts <packagename> works around this, so I think people should run that instead if possible, or install without wheels.

I think @RonnyPfannschmidt will do the last release, so I'd say his decision if he wants to upload wheels for that or not. I don't know if it's possible to test wheels but not release them to PyPI with devpi and our releasing workflow though, at least testing them would be desirable I think...

[nicoddemus]

Closing this, as it seems it will be fixed in 2.7.11.