gh-83004: Clean up refleak in _io initialisation (#98840)

Author: hauntsaninja

Misc/NEWS.d/next/Library/2022-11-02-05-52-36.gh-issue-83004.LBl79O.rst

@@ -0,0 +1 @@
+Clean up refleak on failed module initialisation in :mod:`_io`.

Modules/_io/_iomodule.c

@@ -703,10 +703,10 @@ PyInit__io(void)
         goto fail;
 
     /* BlockingIOError, for compatibility */
-    Py_INCREF(PyExc_BlockingIOError);
-    if (PyModule_AddObject(m, "BlockingIOError",
-                           (PyObject *) PyExc_BlockingIOError) < 0)
+    if (PyModule_AddObjectRef(m, "BlockingIOError",
+                              (PyObject *) PyExc_BlockingIOError) < 0) {
         goto fail;
+    }
 
     // Set type base classes
     PyFileIO_Type.tp_base = &PyRawIOBase_Type;