[migration] handle non-existing attribute type when adding an entity type
The final type needs to be added to the schema first.
Related to #7569998.
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s entity's classes"""