Define %python_sitelib, %python_sitearch, %python_version, %python_version_nodots
    
    In rpm 4.15 those are no longer defined.
    
    The meaning of "python" is derived from %__python - and that errors by default
    unless user defined.
    
    Example usage:
    
        %global __python /usr/bin/pypy3
    
        ...
    
        %files
        %{python_sitelib}/foo/