@Override
  public void onError(CqEvent aCqEvent) {
    throw new IllegalStateException(
        "Not yet supported.");
  }
An error occurred in the processing of a CQ. This event does contain an error. The newValue and
oldValue in the may or may not be available, and will be null if not available.
geode-cq/src/main/java/org/apache/geode/cache/query/cq/internal/CqListenerImpl.java