Remove macOS stderr suppression

[sbrugman]

contextlib.redirect_stderr works on Mac, no need to additional clause

[sbrugman]

We actually had a subtle bug in the previous implementation: when --show-stderr was provided, the program would exit because None is not a valid contextmanager. The contextlib.nullcontext is an elegant alternative for the time being.

Changes:

• FIX: avoid crash when --show-stderr is passed
• ENH: remove obviated dup2 special suppression for macOS
• CI: Increase verbosity of pytest for more informative errors.
• CI: Test the torchfix binary is available (used by the test)
• TST: Add a test for --show-stderr

[kit1980]

Thanks!
I'll double check on an x86 Mac where the issue was happening.

And I need to follow-up on Instagram/LibCST#944 eventually to fix the root cause...

[sbrugman]

@kit1980 Github Actions also offers macOS x86 runners - I've added that one and the test pass. Windows is also included now.

[kit1980]

I tried this on my x86 macbook, and the suppression doesn't work.
tests/test_torchfix.py::test_stderr_suppression actually passed, but running torchfix . causes tons of noise:

torchfix .
Failed to determine module name for /Users/sdym/repos/pytorch-release/vision/examples/cpp/script_model.py: '/Users/sdym/repos/pytorch-release/vision/examples/cpp/script_model.py' is not in the subpath of '' OR one path is relative and the other is absolute.
Failed to determine module name for /Users/sdym/repos/pytorch-release/vision/.github/process_commit.py: '/Users/sdym/repos/pytorch-release/vision/.github/process_commit.py' is not in the subpath of '' OR one path is relative and the other is absolute.

[sbrugman]

Pity, that version of Mac then probably outputs the stderr to stdout and leaves stderr empty...

[sbrugman]

I should also check the stdout here for the macOS issue.