builds against a python debug library were unreliable and could lead to symbol errors during linking. Setting the `Py_DEBUG` define is necessary when linking against a debug build: https://stackoverflow.com/questions/39161202/how-to-work-around-missing-pymodule-create2-in-amd64-win-python35-d-lib https://docs.python.org/2/c-api/intro.html#debugging-builds https://docs.python.org/3.6/c-api/intro.html#debugging-builds
