Comment 4 for bug 1640300

Looks to be an issue in the PostgreSQL listener. This error will continue and fill up the number of connections to Postgres.

2016-11-07 13:09:48 [maas.websocket.listener] Connection lost.
 Traceback (most recent call last):
   File "/usr/lib/python3/dist-packages/twisted/python/log.py", line 84, in callWithContext
     return context.call({ILogContext: newCtx}, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 118, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
   File "/usr/lib/python3/dist-packages/twisted/internet/posixbase.py", line 610, in _doReadOrWrite
     self._disconnectSelectable(selectable, why, inRead)
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/internet/posixbase.py", line 597, in _doReadOrWrite
     why = selectable.doRead()
   File "/usr/lib/python3/dist-packages/maasserver/listener.py", line 168, in doRead
     handler = self.listeners[notify.channel][0]
 builtins.IndexError: list index out of range