Python 3 was actively antagonistic to Python 2 code for no reason other than to lecture us about how we were doing things wrong, writing code to support 2 and 3 to help transition was dumb etc etc.
For example, in python 2 you could explicitly mark unicode text with u"...". That was actively BLOCKED with python 3.0 which supposedly was about unicode support! The irony was insane, they could of just no-oped the u"". I got totally sick of the "expert" language designers with no real world code shipping responsibilities lecturing me. Every post about this stuff was met by comments from pedantic idiots. So every string had to have a helper function around it. Total and absolute garbage. They still haven't explained to my satisifaction why not support u"..." to allow a transition more easily to 3.
Luckily sanity started prevailing around 3.5 and we started to see a progression - whoever was behind this should be thanked. The clueless unicode everything was walked back and we got % for bytes so you could work with network protocols again (where unicode would be STUPID to force given the installed base). We got u"" back.
By 3.6 we got back to reasonable path handling on windows and the 3 benefits started to come without antagonistic approaches / regressions from 2. But that was about 8 years? So that burnt a lot of the initial excitement.
