The lessons have not arrived at the current Python cabal. They just deprecated unittest and are seriously considering to break parts of the C-API again.
For the people who work in the correct companies this will generate many billable hours for no gain.
For others it will be a lot of unpaid work again. At this stage Python should be forked.
> At this stage Python should be forked.
I seriously (I mean seriously) thought about forking Py2 (Tauthon is great BTW) but then I found out that PyPy has a Python2 mode and will for the foreseeable future. Just to be clear: PyPy runs Python 2 code, and always will. (As far as I know. Although it occurs to me that I have no idea what it's like if you're trying to work with the C API.)
(Also I got into Prolog, but that's another story.)
Where has unittest been deprecated?
Some dead horses need a serious beating every now and then to remind people that they can resurrect if you're not careful. All of the lessons the python team did not put into practice were well known at the time, but they knew better and here we are.
The day after tomorrow someone will make breaking changes to some API, framework, language or OS who still needs to learn this lesson, maybe we'll get to them in time.