As discussed on python-dev, add a mechanism to indicate features
that are in the process of deprecation (PendingDeprecationWarning).
Docs could be improved.
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index e2e2629..fa5634a 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -66,6 +66,7 @@
extern DL_IMPORT(PyObject *) PyExc_Warning;
extern DL_IMPORT(PyObject *) PyExc_UserWarning;
extern DL_IMPORT(PyObject *) PyExc_DeprecationWarning;
+extern DL_IMPORT(PyObject *) PyExc_PendingDeprecationWarning;
extern DL_IMPORT(PyObject *) PyExc_SyntaxWarning;
extern DL_IMPORT(PyObject *) PyExc_OverflowWarning;
extern DL_IMPORT(PyObject *) PyExc_RuntimeWarning;