public void addErrors(ErrorHit errorHit) {
        if (this == errorHit) return;
        for (Iterator<? extends ErrorMessage> i = errorHit.errorIterator(); i.hasNext();) {
            addError(i.next());
        }
    }
Add all errors from another error hit to this
container-search/src/main/java/com/yahoo/search/result/DefaultErrorHit.java