Remove code from setuptools pkg that is already in the shipped version of distutils?

[twmr]

I stumbled upon code in the setuptools.command pkg that is already part of setuptools._distutils.command in the setuptools repo. How should we proceed with removing the code duplication? Does it make sense to create a PR that removes duplicated code from the setuptools.command pkg?

[jaraco]

Until Setuptools can rely on every user using the local copy of distutils, Setuptools still needs to support distutils as found in its supported Python versions (3.5+). If the code is already in Python 3.5.0, then it can be removed from Setuptools.