[pkg] Add new autopkgtest for skeleton packaging
When running `cubicweb-ctl newcube`, the generated template provides
debian packaging. So let's add automated tests for that using
autopkgtest.
The new test will generated a new cube, build a source tarball,
build the package, try to install it, see if the Python 3 module is
available and even run autopkgtest against the newly created packages.
Along the way it will also print information about the generated
package: buildinfo, package content, and lintian report.
extend-diff-ignore = "^(__pkginfo__\.py$|doc/_themes/cubicweb/static/(logo-cubicweb-small\.svg|cubicweb\.ico|logo-cubicweb\.svg)$|cubicweb/(sobjects/test/data/(cubicweb_comment|cubicweb_card)|server/test/data-migractions/(migratedapp/)?(cubicweb_comment|cubicweb_localperms|cubicweb_basket|cubicweb_tag|cubicweb_card|cubicweb_file)|test/data-rewrite/(cubicweb_localperms|cubicweb_card))$|cubicweb\.spec$|setup\.cfg$|cubicweb/misc/cwfs)"