[book] Some tweaks to fix cubicweb-documentation package generation
- Fix up PYTHONPATH setting to make sure sphinx can find cubicweb modules
- Add a few missing build-dependencies
# -*- 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"""