Open Stack

The cells v2 effort is going to be introducing a new database into 
Nova.  This has been an opportunity to rethink and approach a few things 
differently, including how we should handle migrations. There have been 
discussions for a long time now about switching over to alembic for 
migrations so I want to ask, should we start using alembic from the 
start for this new database?

The question was first raised by Dan Smith on 
https://review.openstack.org/#/c/135424/

I do have some concern about having two databases managed in two 
different ways, but if the details are well hidden behind a nova-manage 
command I'm not sure it will actually matter in practice.