Create python2 and python3 subpackages (RHBZ#1453189).
    
    Also fix directory ownership of the python2 package directory, based
    on guidance from https://fedoraproject.org/wiki/Packaging:Python .
    
    Also fix the ‘rpmbuild --without ocaml’ case.
    
    (cherry picked from commit 0f3960b876017a1e7682bdf72a4e7e7a2fe6cb14)