class MyError extends Error {}
    CyclicBarrier barrier = new CyclicBarrier(2);
    // we need to make sure the error gets thrown on a different thread.
    ExecutorService service = newSingleThreadExecutor();
    try {
      SequentialExecutor executor = new SequentialExecutor(service);
      Runnable errorTask =
          () -> {
            throw new MyError();
          };

    class MyError extends Error {}
    CyclicBarrier barrier = new CyclicBarrier(2);
    // we need to make sure the error gets thrown on a different thread.
    ExecutorService service = newSingleThreadExecutor();
    try {
      SequentialExecutor executor = new SequentialExecutor(service);
      Runnable errorTask =
          () -> {
            throw new MyError();
          };