code: function (driver, response, remote, options, deferred) {
        // Provide a default error handler to prevent hangs.
        if (!remote.onError) {
          remote.onError = function (request, remote, options, deferred, data) {
            data = JSON.parse(data);
            var value = -1;
            if (typeof data.value.message === 'string') {
              var msg = JSON.parse(data.value.message);
              value = msg.errorMessage;
            }
            deferred.resolve(JSON.stringify({'sessionId': data.sessionId, value: value}));
          };
        }
        remote.onError.call(this, response, remote, options, deferred, this.data);
        return this;
      }
docs: On error callback function
  
  @method _onError
  @param {DalekJs.Internal.Driver} driver Driver instance
  @param {object} response Response from the webdriver server
  @param {object} remote Dummy request body (function name, url, method)
  @param {object} options Request options (method, port, path, headers, etc.)
  @param {object} deferred Webdriver command deferred
  @chainable
  @private