calendar utils: Handle calendar sync fails

calendar_utils/management/commands/update_callendars.py

@@ -7,6 +7,13 @@ class Command(BaseCommand):
     def handle(self, *args, **options):
         self.stdout.write("Updating calendars...")
         for cal in Calendar.objects.all():
-            self.stdout.write(f"+ {cal.url}")
-            cal.update_source()
+            self.stdout.write(f"@ {cal.url}")
+            try:
+                cal.update_source()
+                self.stdout.write("+ ok")
+            except Exception as e:
+                # TODO logging
+                self.stdout.write("- failed")
+                self.stderr.write(e)
+
         self.stdout.write("Updating calendars finished!")