def test_concurrentUsage(self):
        self.lock.lock()
        self.clock.callLater(1, self.lock.unlock)

        d = self.lock.deferUntilLocked()
        d2 = self.lock.deferUntilLocked()

        self.assertFailure(d2, defer.AlreadyTryingToLockError)

        self.clock.advance(1)

        return d
Test that an appropriate exception is raised when attempting
dataset/ETHPy150Open kuri65536/python-for-android/python-modules/twisted/twisted/test/test_defer.py/DeferredFilesystemLockTestCase.test_concurrentUsage