test_regrtest creates temporary test files called test_regrtest_pid_xxx.py in Lib/test/. The problem is that some tests like test___all__ and test_zipfile haves test relying on the list of Lib/test/test_*.py.

When tests are run in parallel, test_regrtest can creates temporary test_regrtest_pid_xxx.py files, test_zipfile sees them, test_regrtest removes them, and then test_zipfiles fails.

The best would be to write these temporary files into a temporary directory, but I failed to fix Lib/test/regrtest.py to load tests from a different directory. In theory, Python 3 supports packages with files splitted into multiple directories, in practice it doesn't seem to work :-p

Maybe test_regrtest should use a test submodule like Lib/test/temp_regrtest/ ?

test_regrtest started to create temporary test_xxx.py files since issue #25220. (Other changes to test_regrtest: issues #18174, #22806, #25260, #25306,  #25369, #25373, #25694).

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ERROR: test_all (test.test___all__.AllTest)
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Traceback (most recent call last):
  File "/home/haypo/prog/python/default/Lib/test/test___all__.py", line 102, in test_all
    with open(path, "rb") as f:
FileNotFoundError: [Errno 2] No such file or directory: '/home/haypo/prog/python/default/Lib/test/test_regrtest_25743_noop20.py'

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