[debian] Update description of cubicweb-ctl* packages init scripts are no longer shipped. Avoid mentionning "start" and "stop" command which should not be used in production environments.

[debian] Introduce a cubicweb-ctl3 binary package This packages conflicts with cubicweb-ctl binary which uses the python2 library. It is meant to ease upgrade of existing installation during the migration from python2 to python3: in particular, by installing cubicweb-ctl3, scripts calling "cubicweb-ctl" command should still work as before.

[cubicweb-ctl] respect sys.exit status code when aborting a command When exploring the stack of all calls to a cubicweb-ctl command, it has been discovered than on a KeyboardInterrupt and on a SystemExit exception the base class InstanceCommand (for commands that works on one instance) will always set the return code of cubicweb-ctl to 8: this mean that if another command do a `sys.exit(some_code)` the exit code will be ignored and overwritten by '8'. This behavior is not intuitive, apparently not documented and doesn't seems to have any justification. It also prevent commands from exciting with different return codes which could be a desired behavior in the situation of scripting.

[test] Add an "actionverb" attribute to test commands

[test] use self.assertRaises() in cwctl tests

[test] ensure mocking is stopped in cwctl tests Either use a decorator or ensure that cleanup is performed. This is so as to prevent global state modification.

[cubicweb-ctl] add '--pdb' global option to launch (i)pdb on exception

[test] Rename TestCommand to avoid PytestCollectionWarning

[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 2 and 3 modules are 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.

[skeleton] Update Debian packaging template 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. * Add Python 3 packages. * Name the binary packages `python-cubicweb-CUBENAME` and `python3-cubicweb-CUBENAME` instead of just `cubicweb-CUBENAME` (which is still the source package). * Populate Depends using dh_python{2,3} 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.