code: function errNameFromCode(code) {
  
      assert.number(code, 'code');
  
      // attempt to retrieve status code description, if not available,
      // fallback on 500.
      var errorDesc = http.STATUS_CODES[code] || http.STATUS_CODES[500];
      return errNameFromDesc(errorDesc);
  }
docs: ------------------------------------------------------------------------------ helpers ------------------------------------------------------------------------------ 
  create an error name from a status code. looks up the description via
  http.STATUS_CODES, then calls createErrNameFromDesc().
  @private
  @function errNameFromCode
  @param {Number} code an http status code
  @returns {String}