Message 353884 - Python tracker

> Or even fatal error out?  There's no reason to have Py_TPFLAGS_HAVE_GC but not implement tp_traverse, AFAIR.

Well... It would prefer a smooth transition.

Such sanity checks which mostly concerns developers perfectly fit the -X dev mode.

I mean, calling Py_FatalError() only in development mode would be acceptable, rather than blocking the usage of C extensions which are working "perfectly well" on Python 3.7.