Fix windows unit tests

[xavfernandez]

• All unit tests seem to pass on windows 2.7
• A peculiar error seems to happen on 3.3/3.4: https://ci.appveyor.com/project/xavfernandez/pip/build/1.0.44/job/jpdg33yn3hccuaxe it's unclear why it only happens on windows, cc @pfmoore
• Something seems off with py35 :-/

[pfmoore]

Well, the error is

        with _secure_open_write(lock.path, self.filemode) as fh:
            fh.write(value)
            TypeError: 'str' does not support the buffer interface

and value is a string:

    cache = SafeFileCache(cache_dir)
    cache.set("foo", "bar")

But see https://github.com/pypa/pip/blob/develop/pip/_vendor/cachecontrol/caches/file_cache.py#L44 - _secure_open_write opens the file in binary mode.

This seems like it's a simple bug, nothing to do with Windows (although maybe there's some oddity in Unix that means the error isn't getting picked up there?)

[xavfernandez]

This seems like it's a simple bug, nothing to do with Windows (although maybe there's some oddity in Unix that means the error isn't getting picked up there?)

Yes it seems simple but there should be no difference for unix/windows :'(

[pfmoore]

Agreed. But I'd focus on working out why the test doesn't fail on Unix first, as I think it should. Even if you confirm that the Unix behaviour is correct, then knowing why should help work out what's wrong on Windows.

[xavfernandez]

@pfmoore The test actually makes the directory unavailable before calling cache.set("foo", "bar") making it a no-op: the test does not even attempt to write.

But on Windows os.chmod does not make the directory unavailable, meaning the cache is used and the tests crashed.

"Fixed" it via a063654

[pfmoore]

Ah, I see. Yes, chmod doesn't do that on Windows (indeed, chmod is largely meaningless on Windows, the Windows permission model is very different from the Unix one). Nice catch.

[xavfernandez]

Also caught an issue with os.path.samefile thanks to appveyor :)

But for the failing tests with python3.5 it looks more like a pytest issue: https://ci.appveyor.com/project/xavfernandez/pip/build/job/vb2mx08p8rkjo056

So I think I'll merge it as is. Maybe we could add a hook on pypa/pip for the unit tests on windows without 3.5 ? (This would have caught the samefile issue).

[xavfernandez]

It looks like it was fixed in pytest-dev/pytest@b18e643 so pytest-2.7.3 .

And of course we are pinned to 2.7.2 due to pytest-dev/pytest#1083 😐

[xavfernandez]

Merged this as is, to have xavfernandez@b47c144 in pip 8.0.
The unit tests seem to pass, it would be good to add an appveyor link when we will be able to unpin pytest and have the unit tests pass on all supported versions.