code: function getResponseDataJson(error, data) {
    var response = null;
    try {
      response = $.parseJSON(data);
    } catch (e) {
      error = '' + e;
    }
    if (response && response.error_class) {
      error = response.error_class + ': ' + response.error_message;
      setButter('Error -- ' + error, true, response.error_traceback);
    } else if (!response) {
      setButter('Error -- Could not parse response JSON data.', true);
    } else {
      return response;
    }
    return null;
  }
docs: Given an AJAX error message (which is empty or null on success) and a data payload containing JSON, parses the data payload and returns the object. Server-side errors and AJAX errors will be brought to the user's attention if present in the response object