def test_maybeDeferredAsyncError(self):
        """
        L{defer.maybeDeferred} should let L{defer.Deferred} instance pass by
        so that L{failure.Failure} returned by the original instance is the
        same.
        """
        d = defer.Deferred()
        d2 = defer.maybeDeferred(lambda: d)
        d.errback(failure.Failure(RuntimeError()))
        self.assertImmediateFailure(d2, RuntimeError)

        L{defer.maybeDeferred} should let L{defer.Deferred} instance pass by
        so that L{failure.Failure} returned by the original instance is the
        same.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_defer.py