private Throwable exceptionOf(Result r) {
        if (r.hits().getError() == null) return null;
        if (r.hits().getError().getCause() == null) return null;
        return r.hits().getError().getCause();
    }
Tests YQL expressions where a list of terms are supplied by indirection

@author bratseth
container-search/src/test/java/com/yahoo/search/yql/TermListTestCase.java