cext: use modern buffer protocol in patches()...
cext: use modern buffer protocol in patches()
PyObject_AsCharBuffer() is part of the "Old Buffer Protocol," which
has been deprecated for years. Let's port away from it.
PyBuffer_GetBuffer() must be paired with PyBuffer_Release(), hence the
added "goto cleanup" in a failure case.
We don't bump the extension version because the API has not changed.
Differential Revision:
https://phab.mercurial-scm.org/D4840
