gh-139322: Create test_os package

[vstinner]

• Move test_posix.py and test_os.py to Lib/test/test_os/
• Split Windows specific test cases to a new test_windows.py file.

• Issue: Tests: move test_posix.py and test_os.py into a new test_os package #139322

[vstinner]

@serhiy-storchaka: Here is a simpler approach which only creates test_windows.py for now.

[serhiy-storchaka]

Were is test_windows?

[vstinner]

Were is test_windows?

Ooops, I forgot git add :-) Fixed.

[serhiy-storchaka]

LGTM. 👍

Win32ErrorTests may be removed if all its tests are duplicated in other places for all platforms.

[serhiy-storchaka]

Originally, these tests were for WindowsError. But now OSError is raised on all platforms. These tests are no longer Windows specific, and most likely are duplicated in other parts.

Please check that all these functions are already tested with non-existing file (and mkdir() with an existing file). Then they can be deleted.

[vstinner]

Merged, thanks for the review.

Win32ErrorTests may be removed if all its tests are duplicated in other places for all platforms.

Good catch! I created #139477 to remove Win32ErrorTests. I prefer to remove the class in a separated change, rather than removing it in the middle of this refactoring (create test_os package).