I think that's unfair. There was plenty of code that was out there for 10 years or more that was working completely fine and had to be ported. One of the most frustrating things I had to do was completely rearchitect some legacy binary file reading/writing because of the changes to how Python handled bytes. That code was out there as open source in the wild, stable, and was being widely used, and it basically required a full rewrite underneath the API.

One of the most frustrating things was that many packages we used as dependencies took ~5 years to port to Python 3, and then dropped Python 2 support immediately, leaving us with no choice but to use the old version for some time. We'd done a lot of the easy stuff already (2to3 on all files), but lots of the non-trivial things were the interactions with other packages so couldn't be touched until they had themselves got a Python 3 version.