Problem: python2 is EOL

[bluca]

python2 is being removed from distros, so all the packaging that uses python2-cffi is starting to be unbuildable.
The packaging rules need to be independent from python2 vs python3, and each conditional on the interpreter version availability, so that we can continue to support distros like RHEL6/CentOS6 independently.
For RPM is easy as OBS supports macros in spec files, but it does not support build profiles for Debian packaging. Adding it to OBS is possible but some non-trivial work.