It has been brought up several times that ET is special in the stdlib in that it is an externally maintained package. Correct me if I'm wrong, but the rules seem to be: features come outside, adaptation to Py3 can happen inside. What we are talking about here is a new feature that makes sense for both Py2 and Py3. We are not talking about a bug fix, neither is this an adaptation to Py3. It is a new feature that was added inside of the standard library and that is not compatible with the external libraries that are supposed to implement the same interface, namely, ElementTree and lxml.etree.