public static <U> EventLoopCheckingFuture<U> exceptionallyCompletedFuture(Throwable cause) {
        requireNonNull(cause, "cause");
        final EventLoopCheckingFuture<U> future = new EventLoopCheckingFuture<>();
        future.completeExceptionally(cause);
        return future;
    }
Returns an {@link EventLoopCheckingFuture} which has been completed exceptionally with the specified
{@link Throwable}.
core/src/main/java/com/linecorp/armeria/common/util/EventLoopCheckingFuture.java