> These changes don't affect gencodec.py, but it may be inconvenient to
> run makeunicodedata.py and gencodec.py using different versions of
> Python.

As MAL explains: these are completely unrelated, independent tools,
and gencodec isn't run more than once per decade (or so). I only ever
run makeunicodedata, and I have been using Python 3 to run it.

The mappings are not supposed to ever change once produced. In
particular, new versions of Unicode cannot affect them, since the
existing characters all map fine to existing code points, which will
not change their meaning per Unicode stability criteria.