> I think it is unreasonable to expect authors of 3rd party modules to respect PEP 384 if the standard library does not.

I don't understand why you think that.  PEP 384 is intended to provide the means to maintain binary compatibility of extension modules so that they don't have to be recompiled for every minor version. Standard library extensions are recompiled for every Python release anyway.

Also, we don't expect authors to respect PEP 384. Either they choose to do so, and get the benefits, or they don't.

> I have simply moved a function from ctypes.c to traceback.c (and renamed it accordingly) so that pyexpat.c can access it.

I can see that. It would be cleaner to do the change in two steps, first move the utility function out from ctypes, then use it from pyexpat.  On the other hand we haven't been adamant about one-patch-one-change in the past.