unittest: fix the _GetOutOf_testPartExecutor exception kind. Fixes …

[qbey]

…#6947

_GetOutOf_testPartExecutor was introduced in
04f27d4
and allow to catch Exception from a unittest TestCase, but as it
inheritate from KeyboardInterrupt it is managed differently by
unittest (see.
https://github.com/python/cpython/blob/032de7324e30c6b44ef272cea3be205a3d768759/Lib/unittest/case.py#L61-L62)
as the testPartExecutor reraise it directly. This prevent unittest to
run the cleanup functions properly.

Since this change enable the teardown methods to be ran properly bu
unittest, the explicit teardown is not required anymore.

Checklist:

• Include documentation when adding new features.
• Include new tests or update existing tests when applicable.
• Allow maintainers to push and squash when merging my commits. Please uncheck this if you prefer to squash the commits yourself.
• Create a new changelog file in the changelog folder, with a name like <ISSUE NUMBER>.<TYPE>.rst. See changelog/README.rst for details.
• Add yourself to AUTHORS in alphabetical order.

[blueyed]

The point of _GetOutOf_testPartExecutor is to get out of there, using KeyboardInterrupt.

I still think that it would be better to revert all that stuff, and require to use pdb.set_trace() for now, FWIW.

See also #6924 #6947.

[qbey]

Thank you Daniel.
Alright, this fix does not preserve the --pdb so it can't be accepted. I close it.
Anyway, the fixup for the cleanup part can't be solved without also considering the async issue, so as said it might be better to revert the original commit for now.

[qbey]

@blueyed You may still want to add the tests (about cleanup and teardown counter), test_cleanup_called_issue6947 fails with pytest 5.4.1 and should not fail with version <5.4.0. So feel free to copy/paste/rewrite them if you rollback your commit :)