Even though I don't fully agree with your comments here is a second
attempt addressing them, against trunk.

For the record, I think that the signature difference is enough to
warrant a name that is a clear cut from PyErr_NewException.
And in the spirit of the Py_InitModule and PyModule_Create families of
function I thought the most common/simple form should stand out from the
more complete one.

But, hey, I'm happy if this gets in (in any form :).