How to generate stop words list from RT index?

Hi! I tried to --buildstops from RT index but got following error:

FATAL: no indexes found in config file ‘/etc/manticoresearch/manticore.conf’

Is there a way to build stop words for RT index?

indexer work only with plain index
you could flush all data from rt index into disk chunk issue optimize with cut=1 option to get only single disk chunk
then use disk chunk from rt index as plain index with some fake definition at the config just provide correct path