I didn't mean to use Django _and_ a separate migration tool. It's just that I did work with Django so far, but switching now to a new codebase without it. Hence my question for experiences in DB migration.
Here we never drop columns, only add new colunms, also never change column types.
When it comes to constraints (not null or something else) we double check about backwards compatibility.
Changing data is not a robust rollback.