Fix deletion of events, don't delete all events

aleksis/apps/untis/util/mysql/importers/events.py

@@ -127,14 +127,14 @@ def import_events(
         existing_events.append(import_ref)
         ref[import_ref] = new_event
 
-        # Delete all no longer existing events
-        for e in LessonEvent.objects.filter(
-            extended_data__event_untis__isnull=False,
-            datetime_start__lte=validity_range.date_end,
-            datetime_end__gte=validity_range.date_start,
-        ):
-            if e.extended_data["event_untis"] not in existing_events:
-                logger.info(f"Event {e.id} deleted")
-                with create_revision():
-                    set_comment(_("Deleted by Untis import"))
-                    e.delete()
+    # Delete all no longer existing events
+    for e in LessonEvent.objects.filter(
+        extended_data__event_untis__isnull=False,
+        datetime_start__date__lte=validity_range.date_end,
+        datetime_end__date__gte=validity_range.date_start,
+    ):
+        if e.extended_data["event_untis"] not in existing_events:
+            logger.info(f"Event {e.id} deleted")
+            with create_revision():
+                set_comment(_("Deleted by Untis import"))
+                e.delete()