'Send an event to a wrapped legacy observer and capture the event as
seen by that observer.
@param event: an event
@type event: L{dict}
@return: the event as observed by the legacy wrapper'

def observe(self, event):

    events = []
    legacyObserver = (lambda e: events.append(e))
    observer = LegacyLogObserverWrapper(legacyObserver)
    observer(event)
    self.assertEqual(len(events), 1)
    return events[0]
