public function deleteContributionAction(Contribution $contribution)
 {
     $em = $this->getDoctrine()->getManager();
     $dir = $this->get('kernel')->getRootDir() . '/../web/';
     unlink($dir . $contribution->getContents());
     $em->remove($contribution);
     $em->flush();
     $response = new Response();
     $response->headers->set('Content-Type', 'application/json');
     return $response;
 }