bpo-34503: Fix refleak in PyErr_SetObject() (GH-8934)

(cherry picked from commit a2eefa6754)

Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>

Python/errors.c

@@ -110,6 +110,7 @@ PyErr_SetObject(PyObject *exception, PyObject *value)
             fixed_value = _PyErr_CreateException(exception, value);
             Py_XDECREF(value);
             if (fixed_value == NULL) {
+                Py_DECREF(exc_value);
                 return;
             }