Fatal error: Uncaught Error: Class "Magento\Checkout\Controller\Onepage" not found in /var/www/magento/html/app/code/BBNT/Checkout/Controller/Cart/Index.php:15 Stack trace: #0 {main} thrown in /var/www/magento/html/app/code/BBNT/Checkout/Controller/Cart/Index.php on line 15