sonderblade: I just noticed your new patch and submission. Looks good at first glance. I'll keep my current patch for myself as I don't think Python 3 will come out just yet, But I'll gladly use your version when it does. I too think it best to get rid of the callback mechanism for the reasons described below, but since I didn't want to be too radical I only added to it. 

Cheers,

Ernest.