leave command unhandled exception

[jahschwa]

This probably happened because the bot was inactive in the XMPP room specified in the chat command. It's likely the logic in determining room is slightly off in the leave command. The result was sending a Matrix room object to the XMPP part_room() method, which raised an unhandled exception.

1. The leave command should catch exceptions from part_room()
2. Audit room determination logic.

2020-04-23 18:08:09 | sibylbot | ERR | Error while executing cmd "leave":
2020-04-23 18:08:09 | sibylbot | ERR |   KeyError: u'!matrixid:domain.net'
2020-04-23 18:08:09 | sibylbot | DEB |   Message text: "#leave xmpp:[email protected]"
2020-04-23 18:08:09 | sibylbot | DEB | Traceback (most recent call last):
  File "/home/sibyl/sibyl/lib/sibylbot.py", line 611, in _cb_message
    reply = func(self,mess,args)
  File "cmds/room.py", line 244, in leave
    proto.part_room(room)
  File "protocols/sibyl_xmpp.py", line 348, in part_room
    if self.mucs[name]['status']==self.MUC_OK:
KeyError: u'!matrixid:domain.net'