Simplify how dicts are turned into fedora-messaging messages
    
    This relies on an utility method added to fedocal-messages in 1.2.0 but
    we've found a bug in that library which has been fixed in 1.4.0 thus the
    dependency on 1.4.0+
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>