pylint: Fix warning and error
    
    - fixed W0612(unused-variable)
    - added missing dependency on python-yaml
    
    Fixes: https://pagure.io/freeipa/issue/8442
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>