If you want the restart, you need to take advantage of the PEP-342 two-way yield(), as in:

    ...
    except SomethingBad:
        yield None 
        restartRequest = yield None
        if restartRequest:
            do whatever is necessary to go on

The problem with the above is that the double yield() ugly. You cannot do this with single yield() because the caller would have to know in advance that next() will return None.