public function loginAction(Request $request, Application $app)
{
$session = $request->getSession();
$error = $app['security.last_error']($request);
$_username = $session->get('_username');
$_password = $session->get('_password');
return $app['twig']->render('demo/login.html.twig', ['error' => $error, '_username' => $_username, '_password' => $_password]);
}