Prints an end message with elapsed time

def end(self, *msg):
        """
        Prints an end message with elapsed time
        """
        if self.start_time is None:
            self.err("No start time set: please use start() "
                     "before using this function")
        endtime = datetime.datetime.now()
        rd = dateutil.relativedelta.relativedelta(endtime, self.start_time)
        endmsg = self._endmsg(rd)
        label = colors.purple("END")
        msg += ("in " + endmsg,)
        self._msg(label, *msg)
        self.start_time = None