This version should bring Python3 compatibility.

We refresh setup.py and __pkginfo__.py using CubicWeb 3.23 skeleton
which is Python3 compatible and still use the legacy layout.

so that pkg_resources can find the package when using a new-style cube

Use pybuild

This is expected for proper caching and will be made mandatory by cubicweb's
722690d7ae28

Closes #16347705

due to conflict on permission with filesystem package (on centos 7)