TypeError: unsupported operand type(s) for -: 'str' and 'int'

[yangxuan8282]

when run on WSL(debian), got this error:

Checking if file exists...
Fetching metadata...
Traceback (most recent call last):
  File "/usr/bin/send-cli", line 124, in <module>
    case_url(args.url)
  File "/usr/bin/send-cli", line 53, in case_url
    file, suggested_name = sendclient.download.send_urlToFile(url, ignoreVersion=args.ignore_version)
  File "/usr/lib/python3.6/site-packages/sendclient/download.py", line 144, in send_urlToFile
    print('The file wishes to be called \'' + metadata['name'] + '\' and is ' + str(jsonMeta['size'] - 16) + ' bytes in size')
TypeError: unsupported operand type(s) for -: 'str' and 'int'