Add exception mode to redirect from object-tag relation type to

object-event relation (generic, e.g. if the tag is actually a time)

exceptions/MDImporterTagRelationTypeIsEventType.php

@@ -0,0 +1,9 @@
+<?PHP
+declare(strict_types = 1);
+
+/**
+ * Exception thrown in case a name entered for the relation between tag
+ * and object is actually an event type.
+ */
+final class MDImporterTagRelationTypeIsEventType extends Exception {
+}