'A generator that calls C{resumeProducing} on the underlying producer
forever.
If C{resumeProducing} throws an exception, the producer is
unregistered, which should result in streaming stopping.'

def _pull(self):

    while True:
        try:
            self._producer.resumeProducing()
        except:
            log.err(None, ('%s    failed,    producing    will    be    stopped:' % (safe_str(self._producer),)))
            try:
                self._consumer.unregisterProducer()
            except:
                log.err(None, ('%s    failed    to    unregister    producer:' % (safe_str(self._consumer),)))
                self._finished = True
                return
        (yield None)
