[OSM-dev] OpenStreetMap Carto dependency changes

[Paul Norman]

OpenStreetMap Carto has changed it's dependencies, which will impact any 
third
parties using the style. The changes are

- Mapnik 3 is now required

- CartoCSS >= 0.16.0 is now required

- Official Tilemill support is dropped. Tilemill does not meet the above 
requirements

- project.mml is now a YAML file which is passed directly to CartoCSS 
without any
   preprocessing

If you are maintaining a fork, rebasing the changes onto your branch 
should be fairly
easy, but you can contact me off-list if you need git help.

The next version released will be v3.0.0. The v3 series is expected to 
be a much
shorter than v2, as we are working on 
https://github.com/gravitystorm/openstreetmap-carto/issues/1504
which will start the v4 series.