public function preRequest(SS_HTTPRequest $request, Session $session, DataModel $model)
 {
     // Bootstrap session so that Session::get() accesses the right instance
     $dummyController = new Controller();
     $dummyController->setSession($session);
     $dummyController->setRequest($request);
     $dummyController->pushCurrent();
     // Block non-authenticated users from setting the stage mode
     if (!Versioned::can_choose_site_stage($request)) {
         $permissionMessage = sprintf(_t("ContentController.DRAFT_SITE_ACCESS_RESTRICTION", 'You must log in with your CMS password in order to view the draft or archived content. ' . '<a href="%s">Click here to go back to the published site.</a>'), Convert::raw2xml(Controller::join_links(Director::baseURL(), $request->getURL(), "?stage=Live")));
         // Force output since RequestFilter::preRequest doesn't support response overriding
         $response = Security::permissionFailure($dummyController, $permissionMessage);
         $session->inst_save();
         $dummyController->popCurrent();
         // Prevent output in testing
         if (class_exists('SapphireTest', false) && SapphireTest::is_running_test()) {
             throw new SS_HTTPResponse_Exception($response);
         }
         $response->output();
         die;
     }
     Versioned::choose_site_stage();
     $dummyController->popCurrent();
     return true;
 }