code: function(responseObject) {
                  responseObject = responseObject || {};
  
                  if (responseObject.xhr) {
                      return responseObject.xhr.getResponseHeader('Location');
                  } else if (responseObject.response && responseObject.response.headers.location) {
                      return responseObject.response.headers.location;
                  }
              }
docs: Extracts the location header
  @param {Promise} responseObject response from a requestXHR
  @returns {String} location header content
  @private