Update to fix build errors with mapnik 3.0.23, along with other pending upstream commits. Upstream has not tagged a python-mapnik release since 2017. This unstable commit, however, is also the basis for the python-mapnik package in Debian testing.
* treewide: remove unused variables * making ofborg happy
Lots of URLs were HTTP redirect to HTTPS. Changed those and checked them if there's actual content. Inspired by https://github.com/NixOS/nixpkgs/issues/60004
fallout of https://github.com/NixOS/nixpkgs/pull/54182