Some fixes for zbar-python build
    
    In order to be able to build a zbar-python, we need to address
    some small things. Among them, there's a requirement to use
    "python3" at python's test script.
    
    IMHO, that's a bad idea, at least upstream, as the same script also
    works with python2 when using pygtk (also supported by ZBar).
    
    Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>