Don't call mapper() outside of declarative registry
Resolve the following RemovedIn20Warning:
Calling the mapper() function directly outside of a declarative
registry is deprecated. Please use the
sqlalchemy.orm.registry.map_imperatively() function for a classical
mapping.
Change-Id: I92a7ccdd48eedd4c788384033743daf50a9dc113
Signed-off-by:
Stephen Finucane <stephenfin@redhat.com>