'Iterate over all clients in a threadpool.
Args:
func: A function to call with each client urn.
max_threads: Number of threads to use.
token: Auth token.
Raises:
RuntimeError: If function not specified.'

def __init__(self, func=None, max_threads=10, token=None):

    self.thread_pool = threadpool.ThreadPool.Factory(self.THREAD_POOL_NAME, max_threads)
    self.thread_pool.Start()
    self.token = token
    self.func = func
    self.broken_subjects = []
    self.out_queue = Queue.Queue()
