gh-128377: Fix test_cmd_line.test_non_interactive_output_buffering fail with PYTHONUNBUFFERED=1

[WolframAlph]

• Issue: test_cmd_line.test_non_interactive_output_buffering fails when PYTHONUNBUFFERED is enabled #128377

[ZeroIntensity]

We should use os_helper.EnvironmentVarGuard() instead of manually messing with os.environ.

[picnixz]

We should use os_helper.EnvironmentVarGuard() instead of manually messing with os.environ.

Thanks for this one. I didn't know whether we had something like that somewhere but you found what I wanted to emulate with mock.patch.dict.

[WolframAlph]

@ZeroIntensity thanks for pointing to that

[picnixz]

LGTM (for reviewers, it's easier to hide whitespace changes).

[ZeroIntensity]

This works, but feels kind of hacky. Why not just unittest.skipIf(os.environ.get("PYTHONUNBUFFERED"))? (Also I'd like to hear @picnixz's preference.)

[picnixz]

Now that you're raising this issue, I'd actually prefer skipping it. If the test is broken when you use PYTHONUNBUFFERED=1 (broken because of unsatisfied pre-requirements, namely it could never work with this configuration), then it's probably fine to just skip it. Changing locally the environment is like saying "hey, you run the test suite with this configuration, but this test is not compatible with that configuration, so we'll temporarily change your configuration so that the test can run".

So yes, let's just skip the test.

[WolframAlph]

Sorry linter failed, did not have pre-commit hooks installed. Will fix asap

[picnixz]

Thanks. I'll merge this one tomorrow (I'll write a nice commit message).

[ZeroIntensity]

Having fun with your commit privileges already I see 😄