def __next__(self):
<EOL>if len(self.active_clients) == <NUM_LIT:0>:<EOL><INDENT>raise ClusterEmptyError("<STR_LIT>")<EOL><DEDENT>self._prune_penalty_box()<EOL>for client in self.clients:<EOL><INDENT>if client in self.active_clients:<EOL><INDENT>return client<EOL><DEDENT><DEDENT>
Always returns a client, or raises an Exception if none are available.