def test_private_timeout(self):
deferred = TimedDeferredLock()
mock = Mock(errback=Mock())
deferred._timeout(mock)
self.assertEqual(mock.errback.call_count, 1)
keywords = mock.errback.mock_calls[0][2]
self.assertIn("fail", keywords)
self.assertIsInstance(keywords["fail"], LockTimeoutError)
