测试paho.mqtt.testing的时候发现这个用例报错呢，Subscribe failure test about server HOT 4 CLOSED

nosubscribe_topics = ("test/nosubscribe",)
//...

def test_subscribe_failure(self):
      # Subscribe failure.  A new feature of MQTT 3.1.1 is the ability to send back negative reponses to subscribe
      # requests.  One way of doing this is to subscribe to a topic which is not allowed to be subscribed to.
      print("Subscribe failure test starting")
      succeeded = True
      try:
        callback.clear()
        aclient.connect(host=host, port=port, keepalive=60)
        print('topic:', nosubscribe_topics[0])
        aclient.subscribe([nosubscribe_topics[0]], [2])
        time.sleep(.2)
        # subscribeds is a list of (msgid, [qos])
        assert callback.subscribeds[0][1][0] == 0x80, "return code should be 0x80 %s" % callback.subscribeds
      except:
        traceback.print_exc()
        succeeded = False
      print("Subscribe failure test", "succeeded" if succeeded else "failed")
      self.assertEqual(succeeded, True)
      return succeeded

  - remote: 10.*:* 
    allow: true
acl:
  #0 = deny, 1 = read only, 2 = write only, 3 = read and write
  - filters:
      'test/nosubscribe': 0```