This forces us to base the Debian package on the source of the Python
package (as produced by running `python3 setup.py sdist`). While
it might seem cumbersome, this greatly reduces likelyhood of mismatch
between an installation via `pip` and one using the Debian package.

`dpkg-source` will also document for us what is currently in the
source repository but not in the Python package. Currently the missing
file are:

PKG-INFO
cubicweb/sobjects/test/data/cubicweb_comment/schema.py
cubicweb/sobjects/test/data/cubicweb_comment/__init__.py
cubicweb/sobjects/test/data/cubicweb_comment/__pkginfo__.py
cubicweb/sobjects/test/data/cubicweb_card/schema.py
cubicweb/sobjects/test/data/cubicweb_card/entities.py
cubicweb/sobjects/test/data/cubicweb_card/__init__.py
cubicweb/sobjects/test/data/cubicweb_card/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_comment/schema.py
cubicweb/server/test/data-migractions/cubicweb_comment/__init__.py
cubicweb/server/test/data-migractions/cubicweb_comment/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_localperms/schema.py
cubicweb/server/test/data-migractions/cubicweb_localperms/__init__.py
cubicweb/server/test/data-migractions/cubicweb_localperms/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_basket/schema.py
cubicweb/server/test/data-migractions/cubicweb_basket/__init__.py
cubicweb/server/test/data-migractions/cubicweb_basket/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_comment/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_comment/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_comment/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_localperms/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_localperms/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_localperms/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_basket/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_basket/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_basket/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_tag/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_tag/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_tag/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_card/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_card/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_card/__pkginfo__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_file/schema.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_file/__init__.py
cubicweb/server/test/data-migractions/migratedapp/cubicweb_file/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_tag/schema.py
cubicweb/server/test/data-migractions/cubicweb_tag/__init__.py
cubicweb/server/test/data-migractions/cubicweb_tag/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_card/schema.py
cubicweb/server/test/data-migractions/cubicweb_card/__init__.py
cubicweb/server/test/data-migractions/cubicweb_card/__pkginfo__.py
cubicweb/server/test/data-migractions/cubicweb_file/schema.py
cubicweb/server/test/data-migractions/cubicweb_file/__init__.py
cubicweb/server/test/data-migractions/cubicweb_file/__pkginfo__.py
cubicweb/test/data-rewrite/cubicweb_localperms/schema.py
cubicweb/test/data-rewrite/cubicweb_localperms/__init__.py
cubicweb/test/data-rewrite/cubicweb_localperms/__pkginfo__.py
cubicweb/test/data-rewrite/cubicweb_card/schema.py
cubicweb/test/data-rewrite/cubicweb_card/entities.py
cubicweb/test/data-rewrite/cubicweb_card/__init__.py
cubicweb/test/data-rewrite/cubicweb_card/__pkginfo__.py

The current manifest will duplicate several files that are stored as
symlinks in the Mercurial repository, hence the long list of ignored
files in `extend-diff-ignore`.