If sys.exit is called or SystemExit raised, don't display success
    
    If sys.exit is called, which raises SystemExit, the finally at the
    end of the installer was treating it as a successful install and
    displaying messages to the user. Catch this exception and mark
    the install as failed to prevent this.
    
    https://fedorahosted.org/ipsilon/ticket/66
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>