Fatal error: Call to undefined method OCP\App::register()

[MafiaInc]

Hello,

I have tried this app on OC 9.0.0 and I got the following error when trying to enable the app:
PHP Fatal error: Call to undefined method OCP\App::register() in /usr/local/www/owncloud/ap
ps/user_wordpress/appinfo/app.php on line 52