gh-109295: Skip test_generated_cases if different mount drives

[vstinner]

On Windows, skip the test if the current working directory and the Python source code directory have different mount drives. It happens if the temporary directory is on a different mount drive than the Python source code.

• Issue: test_asyncio and test_compileall leak temporary files/directories #109295

[vstinner]

Example without the fix:

vstinner@WIN C:\victor\python\main>cd
C:\victor\python\main

vstinner@WIN C:\victor\python\main>python -m test test_generated_cases --tempdir=E:\TEMP\ -j1
Running Debug|x64 interpreter...
0:00:00 Run tests in parallel using 1 child processes
0:00:00 [1/1/1] test_generated_cases failed (uncaught exception)
test test_generated_cases crashed -- Traceback (most recent call last):
  (...)
  File "C:\victor\python\main\Lib\test\test_generated_cases.py", line 11, in <module>
    import generate_cases
  File "C:\victor\python\main\Tools\cases_generator\generate_cases.py", line 41, in <module>
    DEFAULT_INPUT = os.path.relpath(os.path.join(ROOT, "Python/bytecodes.c"))
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\victor\python\main\Lib\ntpath.py", line 791, in relpath
    raise ValueError("path is on mount %r, start on mount %r" % (
ValueError: path is on mount 'C:', start on mount 'E:'

== Tests result: FAILURE ==

1 test failed:
    test_generated_cases

Total duration: 793 ms
Total tests: run=0
Total test files: run=1/1 failed=1
Result: FAILURE

With the fix:

vstinner@WIN C:\victor\python\main>cd
C:\victor\python\main

vstinner@WIN C:\victor\python\main>python -m test test_generated_cases --tempdir=E:\TEMP\ -j1
Running Debug|x64 interpreter...
0:00:00 Run tests in parallel using 1 child processes
0:00:00 [1/1] test_generated_cases skipped
test_generated_cases skipped -- the current working directory and the Python source code directory have different mount drives (E: and C:)

== Tests result: SUCCESS ==

1 test skipped:
    test_generated_cases

Total duration: 613 ms
Total tests: run=0
Total test files: run=1/1 skipped=1
Result: SUCCESS

[miss-islington]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington]

Sorry, @vstinner, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 936376916100681d46db117bae0ec05adf338051 3.11

[miss-islington]

Sorry, @vstinner, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 936376916100681d46db117bae0ec05adf338051 3.12

[vstinner]

Python 3.11 and 3.12 are not affected: Lib/test/test_generated_cases.py is new in Python 3.13.

[vstinner]

An alternative would be to change the current working directory while testing test_generated_cases, as done by test_pyexpat: #109233

But the problem is that the directory should be changed early when test_generated_cases.py is imported, before the first Tools/cases_generator/ import, and the old directory should be restore "later". But when is "later"? After the import? And then change again cwd while running tests using setUpModule()/tearDownModule()?

Well, for me it was too complicated, and I made the minimum fix: just skip the test.