Error while trying to merge UTXOs

[the-tinderbox]

I tried to merge UTXOs with parameters in example

python3.7 btmspanner.py utxomerger -o http://127.0.0.1:9888 -a mining -p 12345 -x 41250000000 -s 0 -m 20 -f 3

I got list of UTXOs to merge and when i confirmed operation, i got error

Traceback (most recent call last):
  File "btmspanner.py", line 13, in <module>
    sys.exit(merge_utxo.main())
  File "/Users/facedsid/htdocs/bytom-spanner/utxomerger/merge_utxo.py", line 152, in main
    print('tx_id:', send_tx(Connection(options.url), utxo_mergelist, to_address, options.password))
  File "/Users/facedsid/htdocs/bytom-spanner/utxomerger/merge_utxo.py", line 78, in send_tx
    if signed_transaction['sign_complete']:
TypeError: string indices must be integers