AZ617: Something is built on a masked view that can't be replaced in place

A masked view (rules app.docs view app.docs_visible) is what the app reads the table through, so a view or a function of yours may be built on it. Applying, and a migration, replace it in place and what is built on it goes on working. That needs the view to keep its columns: here the table's columns changed (one was renamed, say), or the policy no longer has the masked view at all, and Postgres won't drop a view something depends on. The message names what is built on it: drop that, apply (or run the migration) again, then make it again.

Reported when the policy is applied (rowfence push, apply, a migration), against the database.