@Override
  public String getMessage() {
    return String.format("Lucene index %s on region %s already exists.",
        indexName, regionPath);
  }
A LuceneIndexExistsException is thrown if a Lucene index that already exists is attempted to be
created.
geode-lucene/src/main/java/org/apache/geode/cache/lucene/LuceneIndexExistsException.java