The django-multiselectfield package hasn't been maintained in a few years, and it doesn't support Django 4.x+. There's a third-party fork which has had some updates, but no releases that we can consume. django-multiselectfield itself isn't very big, and of what it offers, we don't actually use very much. A new field has been added to Djblets to handle the list serialization/deserialization for comma-separated values. This change switches us over to that. The major differences here are that we have to instantiate the form field ourselves, and the new Djblets field doesn't actually have validation that the entries in the list are part of the choices. The validation isn't important to us because the checkbox widget that Django provides does the right thing for the typical case, and our notifications backend doesn't actually care if there's unknown items in the events list. This also manually sets a max_length on the field. The MultiSelectField would compute the max_length based on the provided choices, but that meant that any change to the choices would need an evolution. Testing Done: - Ran unit tests. - Ran the new evolution. - Tested the WebHookTarget admin form and verified that everything worked as expected.