Bug: _needs_reinstall captures python setup.py --name stderr in addition to stdout

[hashbrowncipher]

I ran into this bug because my setup.py --name uses the warnings module, which prints to stderr. As a result, tox was unable to infer the location of my egg_info directory.

[hashbrowncipher]

This has the side-effect of not showing users the warning that their setup.py presumably wanted seen.

[gaborbernat]

Is #1051 fix for this? Or this is an additional one?

[hashbrowncipher]

This is separate from #1051. I wrote up a failing test case for the behavior I'd like to succeed:

def test_warning_emitted(cmd, initproj):
    initproj(
        "spam-0.0.1",
        filedefs={
            "tox.ini": """
        [testenv]
        skipsdist=True
        usedevelop=True
    """,
            "setup.py": """
        from setuptools import setup
        from warnings import warn
        warn("I am a warning")

        setup(name="spam", version="0.0.1")
    """
        }
    )
    result = cmd()
    result = cmd()
    assert "develop-inst-noop" in result.out

[gaborbernat]

In this case I would propose to print the warning ourselves too, but still continue with the build. Will address.