Fatal error: Uncaught Error: Interface "SMW\Constraint\Constraint" not found in /var/www/html/extensions/SemanticMediaWiki/src/Constraint/Constraints/MandatoryPropertiesConstraint.php:19 Stack trace: #0 {main} thrown in /var/www/html/extensions/SemanticMediaWiki/src/Constraint/Constraints/MandatoryPropertiesConstraint.php on line 19