/**
  * Throw a 403 and redirect to this controller. Replaces Security::permissionFailure()  
  * @param  RequestHandler $c
  * @return SS_HTTPResponse
  */
 public static function permission_failure(RequestHandler $c)
 {
     return $c->redirect(HTTP::setGetVar('BackURL', $_SERVER['REQUEST_URI'], Controller::join_links(Director::baseURL(), 'summit-login', 'login')), 403);
 }