log(info, callback) {
    this._request(info, null, null, (err, res) => {
      if (res && res.statusCode !== 200) {
        err = new Error(`Invalid HTTP Status Code: ${res.statusCode}`);
      }

      if (err) {
        this.emit('warn', err);
      } else {
        this.emit('logged', info);
      }
    });

    // Remark: (jcrugzz) Fire and forget here so requests dont cause buffering
    // and block more requests from happening?
    if (callback) {
      setImmediate(callback);
    }
  }
Core logging method exposed to Winston.
@param {Object} info - TODO: add param description.
@param {function} callback - TODO: add param description.
@returns {undefined}