'Tail this function\'s logs.
if keep_open, do so repeatedly, printing any new logs'

def tail(self, since, filter_pattern, limit=10000, keep_open=True, colorize=True, http=False, non_http=False):

    try:
        since_stamp = string_to_timestamp(since)
        last_since = since_stamp
        while True:
            new_logs = self.zappa.fetch_logs(self.lambda_name, start_time=since_stamp, limit=limit, filter_pattern=filter_pattern)
            new_logs = [e for e in new_logs if (e[u'timestamp'] > last_since)]
            self.print_logs(new_logs, colorize, http, non_http)
            if (not keep_open):
                break
            if new_logs:
                last_since = new_logs[(-1)][u'timestamp']
            time.sleep(1)
    except KeyboardInterrupt:
        try:
            sys.exit(0)
        except SystemExit:
            os._exit(130)
