Traceback (most recent call last):
 File "/opt/stack/quantum/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 769, in <module>
   main()
 File "/opt/stack/quantum/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 763, in main
   plugin.daemon_loop(db_connection_url)
 File "/opt/stack/quantum/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 724, in daemon_loop
   self.rpc_loop()
 File "/opt/stack/quantum/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 705, in rpc_loop
   port_info = self.update_ports(ports)
 File "/opt/stack/quantum/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 610, in update_ports
   ports = self.int_br.get_vif_port_set()
 File "/opt/stack/quantum/quantum/agent/linux/ovs_lib.py", line 245, in get_vif_port_set
   if "iface-id" in external_ids and "attached-mac" in external_ids:
TypeError: argument of type 'NoneType' is not iterable