code: function createRequestTimeoutErr(opts, req) {
      assert.object(opts, 'opts');
      assert.object(req, 'req');
  
      var errInfo = createErrInfo(opts, req);
      var errMsg = [
          opts.method,
          'request to',
          errInfo.fullUrl,
          'failed to complete within',
          opts.requestTimeout + 'ms'
      ].join(' ');
  
      return new ERR_CTOR.RequestTimeoutError({
          info: _.assign(errInfo, {
              requestTimeout: opts.requestTimeout
          })
      }, '%s', errMsg);
  }
docs: build a request timeout error for a request that failed to complete within
  the specified timeout period.
  @private
  @function createRequestTimeoutErr
  @param {Object} opts options object for a request
  @param {Object} req the request object
  @returns {verror.VError} RequestTimeoutError