[dataimport] Drop reference to the 'source' column (closes #4067694).
CW 3.19 drops the multi-source support. This column does not exist in 3.19.
# -*- 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 specific hooks and operations"""