> I definitely think we should not modify any code in the stdlib just to switch to f-strings.

Does this also apply to updating code to use f-strings in an area that's already being modified for a functional purpose? 

I agree that that we shouldn't update stdlib code for the sole purpose of switching to f-strings, but if a function or method is already being changed for another purpose, I don't think updating the formatting to use f-strings is an issue. This would probably have to be decided on a case-by-case basis though.