gh-102192: deprecate _PyErr_ChainExceptions (#102935)

Doc/whatsnew/3.12.rst

@@ -975,6 +975,10 @@ New Features
   This is less error prone and a bit more efficient.
   (Contributed by Mark Shannon in :gh:`101578`.)
 
+* Add ``_PyErr_ChainExceptions1``, which takes an exception instance,
+  to replace the legacy-API ``_PyErr_ChainExceptions``, which is now
+  deprecated. (Contributed by Mark Shannon in :gh:`101578`.)
+
 * Add :c:func:`PyException_GetArgs` and :c:func:`PyException_SetArgs`
   as convenience functions for retrieving and modifying
   the :attr:`~BaseException.args` passed to the exception's constructor.
@@ -1125,6 +1129,8 @@ Deprecated
 * :c:func:`!PyErr_Display` is deprecated. Use :c:func:`PyErr_DisplayException`
   instead. (Contributed by Irit Katriel in :gh:`102755`).
 
+* ``_PyErr_ChainExceptions`` is deprecated. Use ``_PyErr_ChainExceptions1``
+  instead. (Contributed by Irit Katriel in :gh:`102192`.)
 
 Removed
 -------

Include/cpython/pyerrors.h

@@ -98,7 +98,7 @@ PyAPI_FUNC(void) _PyErr_GetExcInfo(PyThreadState *, PyObject **, PyObject **, Py
 
 /* Context manipulation (PEP 3134) */
 
-PyAPI_FUNC(void) _PyErr_ChainExceptions(PyObject *, PyObject *, PyObject *);
+Py_DEPRECATED(3.12) PyAPI_FUNC(void) _PyErr_ChainExceptions(PyObject *, PyObject *, PyObject *);
 PyAPI_FUNC(void) _PyErr_ChainExceptions1(PyObject *);
 
 /* Like PyErr_Format(), but saves current exception as __context__ and

Misc/NEWS.d/next/Core and Builtins/2023-03-31-12-22-25.gh-issue-102192.gYxJP_.rst

@@ -0,0 +1,2 @@
+Deprecated ``_PyErr_ChainExceptions`` in favour of
+``_PyErr_ChainExceptions1``.