DefaultBlockingDispatcherTaskRejectedExecutionException
open class DefaultBlockingDispatcherTaskRejectedExecutionException(val runnable: Runnable, val executor: Executor) : RejectedExecutionException
对 RejectedExecutionException 的扩展, 当 DefaultBlockingDispatcher 将会在追加任务被拒绝时抛出此异常并携带 runnable 和 executor 信息供于外部用户捕获并处理.