PYTHON-2334 Add regression test for gevent.Timeout compatibility

[ShaneHarvey]

This is a follow on to: #472

Before the fixes this test would fail like this:

======================================================================
ERROR: test_gevent_timeout (test.test_client.TestMongoClientFailover)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/shane/git/mongo-python-driver/test/test_client.py", line 1975, in test_gevent_timeout
    self.assertIsNone(ct.get())
  File "src/gevent/greenlet.py", line 769, in gevent._gevent_cgreenlet.Greenlet.get
  File "src/gevent/greenlet.py", line 364, in gevent._gevent_cgreenlet.Greenlet._raise_exception
  File "/Users/shane/git/mongo-python-driver/venv3.8/lib/python3.8/site-packages/gevent/_compat.py", line 65, in reraise
    raise value.with_traceback(tb)
  File "src/gevent/greenlet.py", line 854, in gevent._gevent_cgreenlet.Greenlet.run
  File "/Users/shane/git/mongo-python-driver/test/test_client.py", line 1959, in contentious_task
    coll.find_one({'$where': delay(1)})
  File "/Users/shane/git/mongo-python-driver/pymongo/collection.py", line 1319, in find_one
    for result in cursor.limit(-1):
  File "/Users/shane/git/mongo-python-driver/pymongo/cursor.py", line 1207, in next
    if len(self.__data) or self._refresh():
  File "/Users/shane/git/mongo-python-driver/pymongo/cursor.py", line 1124, in _refresh
    self.__send_message(q)
  File "/Users/shane/git/mongo-python-driver/pymongo/cursor.py", line 999, in __send_message
    response = client._run_operation_with_response(
  File "/Users/shane/git/mongo-python-driver/pymongo/mongo_client.py", line 1368, in _run_operation_with_response
    return self._retryable_read(
  File "/Users/shane/git/mongo-python-driver/pymongo/mongo_client.py", line 1471, in _retryable_read
    return func(session, server, sock_info, slave_ok)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/contextlib.py", line 120, in __exit__
    next(self.gen)
  File "/Users/shane/git/mongo-python-driver/pymongo/mongo_client.py", line 1312, in _slaveok_for_server
    yield sock_info, slave_ok
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/contextlib.py", line 120, in __exit__
    next(self.gen)
  File "/Users/shane/git/mongo-python-driver/pymongo/mongo_client.py", line 1255, in _get_socket
    yield sock_info
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/contextlib.py", line 120, in __exit__
    next(self.gen)
  File "/Users/shane/git/mongo-python-driver/pymongo/pool.py", line 1238, in get_socket
    self.return_socket(sock_info)
  File "/Users/shane/git/mongo-python-driver/pymongo/pool.py", line 1317, in return_socket
    self._socket_semaphore.release()
  File "/Users/shane/git/mongo-python-driver/pymongo/thread_util.py", line 86, in release
    return Semaphore.release(self)
  File "/Users/shane/git/mongo-python-driver/pymongo/thread_util.py", line 64, in release
    self._cond.acquire()
  File "/Users/shane/git/mongo-python-driver/venv3.8/lib/python3.8/site-packages/gevent/thread.py", line 118, in acquire
    acquired = BoundedSemaphore.acquire(self, blocking, timeout)
  File "src/gevent/_semaphore.py", line 143, in gevent._gevent_c_semaphore.Semaphore.acquire
  File "src/gevent/_semaphore.py", line 178, in gevent._gevent_c_semaphore.Semaphore.acquire
  File "src/gevent/_abstract_linkable.py", line 381, in gevent._gevent_c_abstract_linkable.AbstractLinkable._wait
  File "src/gevent/_abstract_linkable.py", line 346, in gevent._gevent_c_abstract_linkable.AbstractLinkable._wait_core
  File "src/gevent/_abstract_linkable.py", line 352, in gevent._gevent_c_abstract_linkable.AbstractLinkable._wait_core
  File "src/gevent/_abstract_linkable.py", line 348, in gevent._gevent_c_abstract_linkable.AbstractLinkable._wait_core
  File "src/gevent/_abstract_linkable.py", line 303, in gevent._gevent_c_abstract_linkable.AbstractLinkable._AbstractLinkable__wait_to_be_notified
  File "src/gevent/_greenlet_primitives.py", line 61, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
  File "src/gevent/_greenlet_primitives.py", line 61, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
  File "src/gevent/_greenlet_primitives.py", line 65, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
  File "src/gevent/_gevent_c_greenlet_primitives.pxd", line 35, in gevent._gevent_c_greenlet_primitives._greenlet_switch
gevent.timeout.Timeout: 10 seconds

----------------------------------------------------------------------
Ran 1 test in 10.015s

FAILED (errors=1)

After the changes in PYTHON-2334 the test passes.

CC: @TylerWilley

[prashantmital]

Nice. LGTM

[ShaneHarvey]

This is blocked on the 3.6+ sharded cluster test failures:

 [2020/07/29 23:37:12.266] ERROR [20.041s]: test_send_hedge (test_read_preferences.TestMongosAndReadPreference)
 [2020/07/29 23:37:12.266] ----------------------------------------------------------------------
 [2020/07/29 23:37:12.266] Traceback (most recent call last):
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/test/__init__.py", line 444, in wrap
 [2020/07/29 23:37:12.266]     return f(*args, **kwargs)
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/test/test_read_preferences.py", line 632, in test_send_hedge
 [2020/07/29 23:37:12.266]     coll.find_one()
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/collection.py", line 1319, in find_one
 [2020/07/29 23:37:12.266]     for result in cursor.limit(-1):
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/cursor.py", line 1207, in next
 [2020/07/29 23:37:12.266]     if len(self.__data) or self._refresh():
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/cursor.py", line 1124, in _refresh
 [2020/07/29 23:37:12.266]     self.__send_message(q)
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/cursor.py", line 1001, in __send_message
 [2020/07/29 23:37:12.266]     address=self.__address)
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/mongo_client.py", line 1372, in _run_operation_with_response
 [2020/07/29 23:37:12.266]     exhaust=exhaust)
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/mongo_client.py", line 1471, in _retryable_read
 [2020/07/29 23:37:12.266]     return func(session, server, sock_info, slave_ok)
 [2020/07/29 23:37:12.266]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/mongo_client.py", line 1366, in _cmd
 [2020/07/29 23:37:12.266]     unpack_res)
 [2020/07/29 23:37:12.267]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/server.py", line 137, in run_operation_with_response
 [2020/07/29 23:37:12.267]     first, sock_info.max_wire_version)
 [2020/07/29 23:37:12.267]   File "/data/mci/720718fde188c25a0d53d0b1c1d3de80/src/pymongo/helpers.py", line 168, in _check_command_response
 [2020/07/29 23:37:12.267]     max_wire_version)
 [2020/07/29 23:37:12.267] pymongo.errors.OperationFailure: Encountered non-retryable error during query :: caused by :: Could not find host matching read preference { mode: "secondary", hedge: { enabled: true } } for set 2b0c4068-ce33-4281-b57e-f67ce1ce77ed, full error: {'ok': 0.0, 'errmsg': 'Encountered non-retryable error during query :: caused by :: Could not find host matching read preference { mode: "secondary", hedge: { enabled: true } } for set 2b0c4068-ce33-4281-b57e-f67ce1ce77ed', 'code': 133, 'codeName': 'FailedToSatisfyReadPreference', '$clusterTime': {'clusterTime': Timestamp(1596065694, 1), 'signature': {'hash': b'vs_\xdb\x0b\xab\xf8\xe6\xbbG\xaa<\xba,\xa2\xc9\xde\xa5\xdc\xb0', 'keyId': 6855047922183045142}}, 'operationTime': Timestamp(1596065694, 1)}
 [2020/07/29 23:37:12.499] ----------------------------------------------------------------------