def test_buildProtocolNoPrimes(self):
        """
        Group key exchanges are not supported when we don't have the primes
        database.
        """
        f1 = self.makeSSHFactory(primes=None)

        p1 = f1.buildProtocol(None)

        self.assertNotIn(
            b'diffie-hellman-group-exchange-sha1', p1.supportedKeyExchanges)
        self.assertNotIn(
            b'diffie-hellman-group-exchange-sha256', p1.supportedKeyExchanges)

        Group key exchanges are not supported when we don't have the primes
        database.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_ssh.py