Fatal error: Uncaught Error: Class "HTMLPurifier_DefinitionCache" not found in /srv/www/htdocs/moodle/lib/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer.php:3 Stack trace: #0 {main} thrown in /srv/www/htdocs/moodle/lib/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer.php on line 3