Use urllib instead of FancyURLopener
    
    Since we're Python 3 only there es no reason to use Six's FancyURLopener
    instead of standard urllib.
    
    FancyURLopener has issues opening Gitea URLs with a custom archive name
    (using the #/archive.tar.gz construction), returning a 404 error instead
    of 200 like urllib.
    
    Signed-off-by: Robert-André Mauchin <zebob.m@gmail.com>