[Distutils] setuptools and use_2to3

I'm trying to convert a setup.py to use setuptools (specifically the docutils build, FWIW). The existing setup.py has some custom command stuff to run 2to3 on build. As I understand it, setuptools should do this automatically by using use_2to3=True. So, I've changed the code to just do: setup( ... packages=find_packages(), use_2to3=True, ... ) However, when I do python setup.py bdist_wheel, I find that docutils/__init__.py within the wheel still contains (for example) class ApplicationError(StandardError): ... So the StandardError -> Exception fixer isn't being run. Am I doing something wrong here? The setuptools documentation isn't very clear on what I should do, or what to expect. Thanks, Paul