Weaken the python3 bindings base package dependency for modular builds
    
    Different parts of libreports are built and shipped with
    different modules in F26 Boltron, namely modules/shared-userspace
    and modules/dnf.  This allows libreport-python3 from modules/dnf
    work with libreport from modules/shared-userspace even though
    they have different dist tags.
    
    This only affects modularity builds and shouldn't be needed
    beyond F26 Boltron.
    
    Signed-off-by: Petr Šabata <contyk@redhat.com>