Using MongoClient causes a deadlock in child after a fork()

test_many_threaded (test_fork.TestFork) ... Exception in thread Thread-230:

Traceback (most recent call last):

  File "/opt/hostedtoolcache/PyPy/3.8.13/x64/lib/pypy3.8/threading.py", line 932, in _bootstrap_inner

    self.run()

  File "/home/runner/work/mongo-python-driver/mongo-python-driver/test/utils.py", line 965, in run

    super(ExceptionCatchingThread, self).run()

  File "/opt/hostedtoolcache/PyPy/3.8.13/x64/lib/pypy3.8/threading.py", line 870, in run

    self._target(*self._args, **self._kwargs)

  File "/home/runner/work/mongo-python-driver/mongo-python-driver/test/test_fork.py", line 156, in fork_behavior

    self.runner.assertEqual(0, os.waitpid(pid, 0)[1])

  File "/opt/hostedtoolcache/PyPy/3.8.13/x64/lib/pypy3.8/unittest/case.py", line 912, in assertEqual

    assertion_func(first, second, msg=msg)

  File "/opt/hostedtoolcache/PyPy/3.8.13/x64/lib/pypy3.8/unittest/case.py", line 905, in _baseAssertEqual

    raise self.failureException(msg)

AssertionError: 0 != 65280

FAIL

...

FAIL: test_many_threaded (test_fork.TestFork)

----------------------------------------------------------------------

Traceback (most recent call last):

  File "/home/runner/work/mongo-python-driver/mongo-python-driver/test/test_fork.py", line 168, in test_many_threaded

    self.assertIsNone(t.exc)

AssertionError: AssertionError('0 != 65280') is not None