protected function registerCacheListener()
    {
        Permission::saved(function () {
            $this->app['cache.store']->forget('permissions.policies');
        });

        Permission::deleted(function () {
            $this->app['cache.store']->forget('permissions.policies');
        });

        Role::saved(function () {
            $this->app['cache.store']->forget('permissions.policies');
        });

        Role::deleted(function () {
            $this->app['cache.store']->forget('permissions.policies');
        });
    }