Ah! I misunderstood the bug report. I was looking for a ENV_FAILED failure, but no, regrtest fails to remove its temporary directory but no warning is emitted in this case.

vstinner@apu$ ls -d build/test_python_*; ./python -m test test_regrtest -m test.test_regrtest.ArgsTestCase.test_crashed; ls -d build/test_python_*
ls: impossible d'accéder à 'build/test_python_*': No such file or directory

Run tests sequentially
0:00:00 load avg: 0.42 [1/1] test_regrtest
1 test OK.

Total duration: 537 ms
Tests result: SUCCESS

build/test_python_816


So running test_regrtest creates build/test_python_816/ but fails to remove it because it contains a core dump: core-python.11.816.

* No core dump must be written, Python is supposed to disable that
* regrtest must emit a warning if it fails to remove the temporary directory, maybe also fail with an error? (non-zero exit code)