We need to PEPify a static format for writing down bootstrap information in Python source trees. The initial target is a list of PEP 508 package requirement strings. It's possible that in the future we might want to add more features like a build system backend specification (as in PEPs 516, 517), or an extension namespace feature to allow third-party developer tools (flit, pytest, coverage, flake8, etc.) to consolidate their configuration in this file in a systematic