Symfony2: captura a exceção no controlador e mostra a mensagem flash

try{
    $em = $this->getDoctrine()->getManager();
    $em->persist($entity);
    $em->flush();

    $this->get('session')->setFlash('notice', 'Article inserted!');
    return $this->redirect($this->generateUrl('article_show', array('id' => $entity->getId())));
}catch(Exception $e){
    // log $e->getMessage()
    $this->get('session')->setFlash('error', 'Can't insert the article.');
}

return $this->render('MyTestBundle:Article:new.html.twig', array(
    'entity' => $entity,
    'form'   => $form->createView(),
));