rpm-build currently depends (via its pythondistdeps.py) on python2 and pulls the entire python2 stack into every buildroot.  Consider switching to smaller, leaner, python3-based and currently always present system-python.  This change will also allow us to ship system-python-only base modules.

The script works fine with Python 3 and system-python & system-python-libs provide everything it needs.

The change is fairly straightforward and only involves changing the shebang line from #!/usr/bin/python to #!/usr/libexec/system-python.

Thanks!