public function executeDeleteUserStorageFile(sfWebRequest $request)
 {
     global $CFG;
     $CFG->current_app->requireMahara();
     $CFG->current_app->requireLogin();
     $form = $request->getPostParameters();
     if ($file = $request->getParameter('file')) {
         $user_storage = new GcrUserStorageAccessS3();
         $user_storage->deleteObject($file);
     }
     $url = $CFG->current_app->getUrl() . '/institution/viewUserStorage';
     $folder = $request->getParameter('key');
     if (isset($folder)) {
         $url .= '?folder=' . $folder;
     }
     $this->redirect($url);
 }