Issue #18711: Add a new PyErr_FormatV function, similar to PyErr_Format but accepting a va_list argument.

Include/pyerrors.h

@@ -242,6 +242,12 @@ PyAPI_FUNC(PyObject *) PyErr_Format(
     const char *format,   /* ASCII-encoded string  */
     ...
     );
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03050000
+PyAPI_FUNC(PyObject *) PyErr_FormatV(
+    PyObject *exception,
+    const char *format,
+    va_list vargs);
+#endif
 
 #ifdef MS_WINDOWS
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithFilename(