*   cause if this Future has failed.
       *
       * - And this future *has* failed: This method is called only from handleException (through
       *   getOrInitSeenExceptions). handleException tried to call setException and failed, so
       *   either this Future was cancelled (which we ruled out with the isCancelled check above),

    EventBus eventBus =
        new EventBus(
            new SubscriberExceptionHandler() {
              @Override
              public void handleException(Throwable exception, SubscriberExceptionContext context) {
                throw new RuntimeException();
              }
            });
    Object subscriber =
        new Object() {
          @Subscribe

  void handleSubscriberException(Throwable e, SubscriberExceptionContext context) {
    checkNotNull(e);
    checkNotNull(context);
    try {
      exceptionHandler.handleException(e, context);
    } catch (Throwable e2) {
      // if the handler threw an exception... well, just log it
      logger.log(
          Level.SEVERE,