Setuptools is supposed to work with PEP 517 just fine with no changes, other than adding the build-backend declaration in pyproject.toml. Old versions of Pip wi

Setuptools is supposed to work with PEP 517 just fine with no changes, other than adding the build-backend declaration in pyproject.toml. Old versions of Pip will find your setup.py and use it directly, and new versions will find it via pyproject.toml and invoke it via `build`. Maybe you hit a bug? Or were doing something unusual and complicated. I never had a problem with the transition in a Setuptools pronect.