Python 2 legacy code on Eagle

[chchang6]

We want to encourage Python 3, but there are cases where Py2 environments or conversions are useful though, particularly for academic offerings written in 2 that will never get ported to 3.

Maybe the user story could be "I need to use an awful Python 2 module that will never be updated to Python 3, how can I do it?" and options (1--find an alternative so you can use up-to-date auxiliary tools; 2--convert to 3 so you can use up-to-date auxiliary tools, include link to https://docs.python.org/3/library/2to3.html; 3--set up a Python 2 custom environment).

Originally posted by @chchang6 in https://github.com/NREL/HPC/issues/26#issuecomment-775396414