def test_waitUntilLockedWithTimeoutUnlocked(self):
        """
        Test that a lock can be acquired while a lock is held
        but the lock is unlocked before our timeout.
        """
        def onTimeout(f):
            f.trap(defer.TimeoutError)
            self.fail("Should not have timed out")

        self.assertTrue(self.lock.lock())

        self.clock.callLater(1, self.lock.unlock)
        d = self.lock.deferUntilLocked(timeout=10)
        d.addErrback(onTimeout)

        self.clock.pump([1] * 10)

        return d

        Test that a lock can be acquired while a lock is held
        but the lock is unlocked before our timeout.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_defer.py