'get a task based on task_name, if queue is empty, raise queue.Empty'

def get_a_task(self, task_name):

    task_content = None
    if (task_name == TPEnum.URL_FETCH):
        task_content = self._fetch_queue.get(block=True, timeout=5)
        self.update_number_dict(TPEnum.URL_NOT_FETCH, (-1))
    elif (task_name == TPEnum.HTM_PARSE):
        task_content = self._parse_queue.get(block=True, timeout=5)
        self.update_number_dict(TPEnum.HTM_NOT_PARSE, (-1))
    elif (task_name == TPEnum.ITEM_SAVE):
        task_content = self._save_queue.get(block=True, timeout=5)
        self.update_number_dict(TPEnum.ITEM_NOT_SAVE, (-1))
    self.update_number_dict(TPEnum.TASKS_RUNNING, (+ 1))
    return task_content
