Fatal error: Uncaught Error: Interface "Sabre\Xml\Element" not found in /var/www/apache/dev/cal/web/vendor/sabre/xml/tests/Sabre/Xml/Element/Mock.php:7 Stack trace: #0 {main} thrown in /var/www/apache/dev/cal/web/vendor/sabre/xml/tests/Sabre/Xml/Element/Mock.php on line 7