def test_channel_callback_stays_active(self, earlyfree=True):

       # with 'earlyfree==True', this tests the "sendonly" channel state.

       l = []

       channel = self.gw.remote_exec(source='''

               import thread, time

               def producer(subchannel):

                   for i in range(5):

                       time.sleep(0.15)

                       subchannel.send(i*100)

               channel2 = channel.receive()

               thread.start_new_thread(producer, (channel2,))

               del channel2

               ''')

->     subchannel = self.gw.newchannel()

       subchannel.setcallback(l.append)

       channel.send(subchannel)

       if earlyfree:

           subchannel = None

       counter = 100

       while len(l) < 5:

           if subchannel and subchannel.isclosed():

               break

           counter -= 1

           print counter

           if not counter:

               py.test.fail("timed out waiting for the answer[%d]" % len(l))

           time.sleep(0.04)   # busy-wait

       assert l == [0, 100, 200, 300, 400]

       return subchannel