Update Python 2.7 in place

[snippsat]

but I have yet to see a supported method for updating the underlying Python 2.7.

No need to update underlying python.
pyenv work for CentOS example.

I understand your explanation,but it make no sense to try to fix that way.
pyenv or the new pipenv is great,and also virtual environment(now also build into 3.6),
should make it easy to avoid conflict you describe.
You just need to look at train using these tools.