def test_verifyBadKey(self):
        """
        L{default.verifyHostKey} should return a L{Deferred} which fails with
        L{HostKeyChanged} if the host key is incorrect.
        """
        d = default.verifyHostKey(
            self.fakeTransport, b"4.3.2.1", otherSampleKey,
            "Again, not required.")
        return self.assertFailure(d, HostKeyChanged)

        L{default.verifyHostKey} should return a L{Deferred} which fails with
        L{HostKeyChanged} if the host key is incorrect.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_knownhosts.py