code: function _extractEmptyResponse(xml, dfrd) {
    var parser = new xml2js.Parser();
    parser.parseString(xml, function(err, res) {
      if (err) {
        dfrd.reject();
        return MODULE_ERRORS.xmlParseError;
      }
      if (res.response.error) {
        dfrd.reject(res.response.error);
      }
    });
  }
docs: Basically just asserts an empty response has no errors in it.
  @param {string} xml XML to parse
  @param {Q.defer} dfrd Q deferred object