code: public static <T> CompletableFuture<T> exceptionalFuture(Throwable t) {
      CompletableFuture<T> future = new AtomixFuture<>();
      future.completeExceptionally(t);
      return future;
    }
docs: Returns a new exceptionally completed Atomix future.
  
  @param t   the future exception
  @param <T> the future result type
  @return the completed future