public function validate(FormEvent $event)
 {
     parent::validate($event);
     $form = $event->getForm();
     if ($form->has('email')) {
         $email = $form->get('email')->getData();
         if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
             $form->get('email')->addError(new FormError("Invalid email address."));
         }
     }
 }