code: func (cms *ConcurrentMergeScheduler) handleMergeError(err error) {
  	// When an exception is hit during merge, IndexWriter
  	// removes any partial files and then allows another
  	// merge to run.  If whatever caused the error is not
  	// transient then the exception will keep happening,
  	// so, we sleep here to avoid saturating CPU in such
  	// cases:
  	time.Sleep(250 * time.Millisecond)
  	// Lucene Java throw Unchecked exception in a separate thread.
  	// GoLucene just dump the error in console.
  	log.Printf("Merge error: %v", err)
  }
docs: /*
  Called when an error is hit in a background merge thread
  */