Though I think the communication has been pretty clear that developers should stop using % formatting in favor of .format when moving to Python 3. Not so much a deviation, just a migration. Now that there's another alternative, there definitely needs to be some clear communication about what's going to be idiomatic going forward.

Except that they went and made .format() useless for bytes... which made everyone have to hang on to % for both 2/3 compatibility cases, and for all the cases where bytes templates were actually needed (all kinda of lowlevel wire protocols and file storage formats).