The patch (to my production Idle, with name fix) prevents crashing and raises an error instead when an object *can* be pickled, so I will apply before 3.3 if no problems appear and we cannot do better.

But written objects are still pickled, so sys.stdout.write(sys) still raises the PicklingError instead of (as in CP interpreter)
  TypeError: must be str, not module

It seems to me that the type check should be done in the subprocess before the object (which should be a string) is pickled. (I also wonder if it is really necessary to pickle a string or the encoded bytes to send it back. The pickle is just a stream of bytes.)