Comment 17 for bug 475465

You only have fixed a symptom here. As a next step, the model needs to be fixed to make the field required. That will prevent the ORM from dropping the constraint on the inherit table.

Additionally, in the longer term, the ORM needs to be fixed to error out in these situations, because PostgreSQL will change to prevent dropping NOT NULL constraints on inherited tables.

I have attached a patch to fix the model, but I am not deep enough into the ORM to fix the actual issue.