@Override
    public void sendError(int status, @Nullable String message) {
        if (committed) {
            throw new IllegalStateException("Already committed");
        }
        final HttpStatus errorStatus = HttpStatus.valueOf(status);
        checkArgument(errorStatus.isError(), "Not an error status: %s", status);
        this.status = errorStatus;
        errorMessage = message;
        committed = true;
    }
Implements {@link org.jboss.resteasy.spi.HttpResponse}.
resteasy/src/main/java/com/linecorp/armeria/server/resteasy/ResteasyHttpResponseImpl.java