I have been trying to update the openstreetmap-carto package, but I am not even sure that the current version works in unstable and testing. I think this is due to the change to mapnik 3. The upstream repository suggests that the style does not work with mapnik 3, and it does not seem to work for me yet (I have been having problems with loading fonts). What needs doing now? Also, how can this be prevented from happening in the future?