GitLab

Here are multiple updates to the Debian packaging template provided when
running `cubicweb-ctl newcube`:

 * Switch to source format 3.0 (quilt).
 * Switch to debhelper 9.
 * Switch to dh-python.
 * Switch to Python 3.
 * Name the binary package `python3-cubicweb-CUBENAME` instead of
   just `cubicweb-CUBENAME` (which is still the source package).
 * Populate Depends using dh_python3 support for Python requirements.
 * Run test suite at build time using pytest.
 * Add autopkgtest to run test suite against the installed package.
 * Bump Standards-Version to 4.3.0.