[pkg] Remove build dependency on dh-systemd As suggested by Lintian, remove build dependency on obsolete package dh-systemd. Instead, specify a more precise version of debhelper 9 that added support for systemd.

[pkg] Run test suite as part of autopkgtest Add support for autopkgtest. The test “unittest” will run the test suite using pytest. As we need PostgreSQL in the test environment and open network connection, the test is marked with `isolation-container` and requires at least LXC to be run, e.g: autopkgtest -s -- lxc -s autopkgtest-sid

[pkg] Switch to Debian source format 3.0 (quilt) 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`.

[pkg] Switch all Debian packages to Python 3