Use any python version for python bindings

Use any python version for python bindings

In order to work on Ubuntu 20.04 which does not have a "python" lib,
only "python3" and "python2".

See https://www.fosslinux.com/26413/ubuntu-20-04-lts-focal-fossa-set-to-remove-python-2.htm.

Also needed was to replace pyversion which found only Python 2
versions. Possibly this can done in a better way by someone who
understands Debian packaging in general and Lintian in particular.

See https://lintian.debian.org/tags/debian-pyversions-is-obsolete.html.