Bug 1354222: Allowing the deletion of group files

Was failing due to not being able to fine artefact files library

behatnotneeded

Change-Id: Ie28d697ffc922d70d86457a8ca4a978dfddaec55
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>

htdocs/artefact/lib.php

@@ -756,6 +756,7 @@ abstract class ArtefactType implements IArtefactType {
             }
         }
 
+        safe_require('artefact', 'file');
         // Delete non-containers grouped by artefacttype
         foreach ($leaves as $artefacttype => $ids) {
             $classname = generate_artefact_class_name($artefacttype);