def test_notImplementedClientMethods(self):
        """
        verifyHostKey() should return a Deferred which fails with a
        NotImplementedError exception.  connectionSecure() should raise
        NotImplementedError().
        """
        self.assertRaises(NotImplementedError, self.klass().connectionSecure)
        def _checkRaises(f):
            f.trap(NotImplementedError)
        d = self.klass().verifyHostKey(None, None)
        return d.addCallback(self.fail).addErrback(_checkRaises)

        verifyHostKey() should return a Deferred which fails with a
        NotImplementedError exception.  connectionSecure() should raise
        NotImplementedError().
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py