Issue #21715: Extracted shared complicated code in the _io module to new
_PyErr_ChainExceptions() function.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 302db0a..8084aae 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -543,20 +543,8 @@
     }
 
     if (exc != NULL) {
-        if (res != NULL) {
-            Py_CLEAR(res);
-            PyErr_Restore(exc, val, tb);
-        }
-        else {
-            PyObject *exc2, *val2, *tb2;
-            PyErr_Fetch(&exc2, &val2, &tb2);
-            PyErr_NormalizeException(&exc, &val, &tb);
-            Py_DECREF(exc);
-            Py_XDECREF(tb);
-            PyErr_NormalizeException(&exc2, &val2, &tb2);
-            PyException_SetContext(val2, val);
-            PyErr_Restore(exc2, val2, tb2);
-        }
+        _PyErr_ChainExceptions(exc, val, tb);
+        Py_CLEAR(res);
     }
 
 end: