Dispatch an event.
               event: name of the event (str)
               ev_msg: non-optional arguments dictionary.
           Side effects:
               If an EventObject is not already registered with the EventManager,
               a new EventObject will be created and registered.

def dispatch(self, event, ev_msg):
        """Dispatch an event.
               event: name of the event (str)
               ev_msg: non-optional arguments dictionary.
           Side effects:
               If an EventObject is not already registered with the EventManager,
               a new EventObject will be created and registered."""
        logger.debug('dispatching: ' + event + ': ' + repr(ev_msg))
        eo = self.events.get(event, None)
        if eo:
            eo.dispatch(ev_msg)