if handler is None:
                    raise HandlerError, \
                    "Required handler for task {} not defined".format(task[1])

                handler = getattr(self, task[1], None)
                if task[1] in self.handlers:
                    handler = self.handlers[task[1]]

try:
    processing = RssProcessing(max_workers=500)
    processing.dispatch(tasks)
except ProcessingError, excobj:
   # обработка одного исключения
except HandlerError, excobj:
   # обработка второго исключения
except HandlerTimeout, excobj:
   # обработка третьего исключения

try:
    processing = RssProcessing(max_workers=500)
    processing.dispatch(tasks)
except ProcessingError, excobj:
    print excobj # тут будет напечатано что именно случилось
    ....

class TimeoutError(Exception):
    pass

class with_timeout(object):
    def __init__(self, timeout):
        self.timeout = timeout

    def __call__(self, func):
        def raiser(signum, frame):
            raise TimeoutError("Timeout expired")

        def wrapped(*args):
            saved = signal.signal(signal.SIGALRM, raiser)
            signal.alarm(self.timeout)
            try:
                func(*args)
            finally:
                signal.signal(signal.SIGALRM, saved)
            signal.alarm(0)
        return wrapped

def document_handler(self, pool, *task):
    foo = task[-1]
    bar = task[-2]
    task_id = task[0]

@with_timeout(4, image_failed)
def image_handler(self, *task):

data = None
with Timeout(5, False):
    data = mysock.makefile().readline()
if data is None:
    ...  # 5 seconds passed without reading a line
else:
    ...  # a line was read within 5 seconds

def document_handler(self, handler, feed_id, category)

    @with_timeout(1, image_handler_failed)
    def image_handler(self, *task):
        '''Complete docs at real implementation!
        Process image. This handler *knows* about document its working with, thats very usefull for consistency
        of document object.

        '''
        self.debug('image_handler on {} started'.format(task[0]))
        document = task[1]
        document['images'].append(task[0])
        sleep(randint(0, 5))
        # decrease number of possible images for this documents that's are awaiting to check
        document['images_cnt'] -= 1
        self.flush_results()
        self.debug('image_handler on {} completed'.format(task[0]))