Remove Python 2 support and packages
    
    Remove Python 2 related code and configuration from spec file, autoconf
    and CI infrastructure. From now on, FreeIPA 4.8 requires at least Python
    3.6. Python 2 packages like python2-ipaserver or python2-ipaclient are
    no longer available. PR-CI, lint, and tox aren't testing Python 2
    compatibility either.
    
    See: https://fedoraproject.org/wiki/Changes/FreeIPA_Python_2_Removal
    Fixes: https://pagure.io/freeipa/issue/7568
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Tibor Dudlak <tdudlak@redhat.com>