protected function findGroupBy($key, $value)
    {
        if (!empty($value)) {
            $group = $this->get('fos_user.group_manager')->{'findGroupBy'.ucfirst($key)}($value);
        }

        if (empty($group)) {
            throw new NotFoundHttpException(sprintf('The group with "%s" does not exist for value "%s"', $key, $value));
        }

        return $group;
    }