Here is the pooling:

for host in ri.get_next_most_crowded_host():
    results = pool.apply_async(self.__get_host_urls, [ri])

And the exception:

Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python3.2/threading.py", line 736, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.2/threading.py", line 689, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.2/multiprocessing/pool.py", line 338, in _handle_tasks
    put(task)
_pickle.PicklingError: Can't pickle <class 'method'>: attribute lookup builtins.method failed

Here is the functions trying to be called:
...
def __get_host_urls(self, ri):
    pool = Comm.ThreadPool(self.poolsize)
    sp = Comm.SocketPool(size=self.poolsize)
    results = []
    for lpi in ri.links[host]:
        pool.add_task(self.__get_url_by_sp, host, self.count, sp, lpi, results)
        self.count += 1
    pool.wait_completion()
    return results

def __get_url_by_sp(self, host, nr, sp, lpi, resultlist):
    try:
        resp = sp.urlopen(nr, host, lpi.url)
        lpi.set_info('html', resp)
        resultlist.append(lpi)
    except Exception as e:
        self.logger.exception(e)
...