The Python 2 to 3 thing was worse when they started: people who made the mistake of falling for the rhetoric to port to python3 early on had a much more difficult time as basic things like u"" were broken under an argument that they weren't needed anymore; over time the porting process got better as they acquiesced and unified the two languages a bit.

I thereby kind of feel like this might have happened in the other direction: a ton of developers seem to have become demoralized by python3 and threw up their hands in defeat of "backwards compatibility isn't going to happen anyway", and now we live in a world with frozen dependencies running in virtual environments tied to specific copies of Python.