docs: function createClient(testRedisUrl) {
    const redisUrl = testRedisUrl || REDIS_URL;
  
    if (!redisUrl) {
      return bluebird.reject(new Error('No Redis URL set'));
    }
  
    log('debug', `Connecting to Redis at ${redisUrl}`);
  
    return new bluebird(resolve => {
      module.exports.client = bluebird.promisifyAll(new Redis(redisUrl));
      module.exports.client.on('error', logGenericError(__filename));
  
      resolve({ server: redisUrl });
    });
  }