code: function(xhr, status, error) {
          delete this.cache[xhr.url];
  
          // Remove loading state
          this.element
              .removeClass('is-loading')
              .addClass('has-failed')
              .aria('busy', false);
  
          this.position(Toolkit.messages.error);
      }
docs: Event handler for AJAX `fail` events when called through `requestData()`.
  
  @param {jQuery.ajax} xhr
  @param {String} status
  @param {String} error