This is not the only comment ITT to recommend Asciidoc. It seems interesting, so I looked into it. On the asciidoc Github page [0], I found this note: "NOTE: This implementation is written in Python 2, which EOLs in Jan 2020. AsciiDoc development is being continued under @asciidoctor."
In other words, upgrading to py3 was such a pain, they rewrote it in Ruby instead. Ouch! This has got to be the worst example (among more than a few) of py3 pain I've seen yet!