It was a fiasco because it wasn't possible (until much later) to support both Python 2 and Python 3 in the same code base. This made for a gridlock between dependencies and users.

This is a misconception that has likely been compounded by the initial advice (by core Python folks, who eventually reverted their stance) on not doing this. For example, see this blog post https://aroberge.blogspot.com/2009/08/crunchy-10-released.ht... from 2009 for a non-trivial program that supported Python 2.4, 2.5, 2.6 and 3.1. It was a bit of a pain as it dealt with lots of unicode/strings, but it was doable. It became easier to support both Python 2 and Python 3 later on, especially once Python 3.2 was released.

Ok, sorry, replace "not possible" with "very difficult and not recommended."

I don't see how that changes what I wrote in a very meaningful way.