Bundled up in the confusion about the PEP 517 rollout is the issue that PEP 517 does not allow for PEP 517 backends to use PEP 517 to build themselves, and how the bootstrapping should take place is left unspecified. This is a problem for setuptools at the moment, and presumably other build backends like flit. Since I know not everyone on this list follows the discourse, I thought it prudent to advertise here that I've created a thread on the Python discourse to discuss this topic: https://discuss.python.org/t/pep-517-backend-bootstrapping/789