def redis(self):
        """
        A :class:`redis.StrictRedis` instance, configured to connect to the
        current application's Redis server.
        """
        redis_url = current_app.config.get("SSE_REDIS_URL")
        if not redis_url:
            redis_url = current_app.config.get("REDIS_URL")
        if not redis_url:
            raise KeyError("Must set a redis connection URL in app config.")
        return StrictRedis.from_url(redis_url)