Edit groups broken with Chronos
(If really chronos-specific, please move issue there.)
Editing groups is broken with:
File "/srv/aleksis/envs/production/lib/python3.9/site-packages/django/forms/forms.py", line 184, in __getitem__
raise KeyError(
KeyError: "Key 'subject_id' not found in 'EditGroupForm'. Choices are: additional_fields, avatar, group_type, members, name, owners, parent_groups, photo, school_term, short_name."