Fatal error: Uncaught Error: Class "HTMLPurifier_ChildDef_Required" not found in /srv/www/htdocs/moodle/lib/htmlpurifier/HTMLPurifier/ChildDef/Optional.php:10 Stack trace: #0 {main} thrown in /srv/www/htdocs/moodle/lib/htmlpurifier/HTMLPurifier/ChildDef/Optional.php on line 10