[...]
I mean, it's great that the rise of languages like Python that have
easy range-checked string manipulation has knocked buffer overflows
out of the #1 spot, but... :-)

Guido is right that the nice thing about classic string interpolation
is that its use in many languages gives us tons of data about how it
works in practice. But one of the things that data tells us is that it
actually causes a lot of problems! Do we actually want to continue the
status quo, where one set of people keep designing languages features
to make it easier and easier to slap strings together, and then
another set of people spend increasing amounts of energy trying to
educate all the users about why they shouldn't actually use those
features? It wouldn't be the end of the world (that's why we call it
"the status quo" ;-)), and trying to design something new and better
is always difficult and risky, but this seems like a good moment to
think very hard about whether there's a better way.

(And possibly about whether that better way is something we could put
up on PyPI now while the 3.6 freeze is still a year out...)