SemLock._cleanup triggers an unraisable exception in Finalizer when a semaphore is manually unlinked first

[ogrisel]

The sl object gets garbage collected and finalized after a manual sem_unlink in test_semlock_failure. This triggers unraisable exception and warning in the pytest report. Furthermore, that prevents the call to resource_tracker.unregister(name, "semlock").

tests/test_synchronize.py::test_semlock_failure
  /Users/ogrisel/mambaforge/envs/dev/lib/python3.10/site-packages/_pytest/unraisableexception.py:78: PytestUnraisableExceptionWarning: Exception ignored in: <Finalize object, dead>
  
  Traceback (most recent call last):
    File "/Users/ogrisel/mambaforge/envs/dev/lib/python3.10/multiprocessing/util.py", line 224, in __call__
      res = self._callback(*self._args, **self._kwargs)
    File "/Users/ogrisel/code/loky/loky/backend/synchronize.py", line 98, in _cleanup
      sem_unlink(name)
  FileNotFoundError: [Errno 2] No such file or directory
  
    warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))