Do not require PyGObject in setup.py
    
    Requiring PyGObject in setup.py causes, that on EPEL7 this component is
    required although it is not listed as a specfile dependency.
    
    Resolves: rhbz#1679365
    JIRA: COMPOSE-3305
    
    Signed-off-by: Ondrej Nosek <onosek@redhat.com>