[multi-sources-removal] Drop entities.source column
Since we remove federated multi-sources support, the same value ('system')
is always stored in this column and so could be removed. Also, cleanup
repository caches and a few api where the very same useless information could
be removed.
Closes #2919300, at last
[jcr: restore sanity check of etype against schema in checkintegrity.has_eid]
# -*- 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"""