GitLab

Update the build system to use pybuild.

The new binary package with Python 3 support is named
python3-cubicweb-bootstrap according to current standards.
Python 2 package is also updated to use the proper namespace
and a transitional package has been introduced to handle
the migration.

Support for Python 3.8 is disabled as it is currently broken
in Debian unstable.

This is invalid rst which prevents upload on pypi.

This should prevent packaging regression such as the one
that occurred recently.

* we include tox.ini (useful to run tests)
* we include all files in doc directory
* we exclude debian directory and .spec file

- F401 'warnings.warn' imported but unused
- E201 whitespace after '('
- E202 whitespace before ')'
- E261 at least two spaces before inline comment

- update __pkginfo__.py to use cubicweb 3.26
- update MANIFEST.in
- remove useless symlink to __pkginfo__.py