"In particular, there are ongoing efforts to try to make it the normal thing for scientists to make the programs they ran on their data available so that their results can be reproduced; aggressively dropping older programming language implementations rather gets in the way of that."

But if this is important to you then depending on the OS to provide your python seems like a bad idea, independent of the python2/python3 issues. Wouldn't it be much better to use something like conda / the anaconda distribution, so that you can specify precise versions of each library for your environment?

Having said that, I don't know how anaconda is going to handle the EOL of python2. So I guess the question is: if someone wants to be able to reliably reproduce a python2 environment with specific set of libraries, what is best way to do that?