tl;dr: Projects still relying on sqlalchemy-migrate for migrations need to start
their switch to alembic immediately. Projects with "legacy" sqlalchemy-migrated
based migrations need to drop them.

A quick heads up that oslo.db 13.0.0 will be release in the next month or so and
will remove sqlalchemy-migrate support and formally add support for sqlalchemy
2.x. The removal of sqlalchemy-migrate support should only affect projects using
oslo.db's sqlalchemy-migrate wrappers, as opposed to using sqlalchemy-migrate
directly. For any projects that rely on this functionality, a short-term fix is
to vendor the removed code [1] in your project. However, I must emphasise that
we're not removing sqlalchemy-migrate integration for the fun of it: it's not
compatible with sqlalchemy 2.x and is no longer maintained. If your project uses
sqlalchemy-migrate and you haven't migrated to alembic yet, you need to start
doing so immediately. If you have migrated to alembic but still have sqlalchemy-
migrate "legacy" migrations in-tree, you need to look at dropping these asap.
Anything less will result in broken master when we bump upper-constraints to
allow sqlalchemy 2.x in Bobcat. I've listed projects in $subject that appear to
be using the removed modules.

For more advice on migrating to sqlalchemy 2.x and alembic, please look at my
previous post on the matter [2].

Cheers,
Stephen

[1] https://review.opendev.org/c/openstack/oslo.db/+/853025
[2] https://lists.openstack.org/pipermail/openstack-discuss/2021-August/024122.html