Twillo Callback Channel Error

Rasa core == 11.2

The twillo callback channel is unable to parse my credentials.yml file and get the account sid;

File "/Users/ahson/Library/Python/2.7/lib/python/site-packages/rasa_core/", line 177, in _create_single_channel
AttributeError: 'NoneType' object has no attribute 'get'

When I run this following command:

python -m -d models/dialogue -u models/current/nlu --endpoints endpoints.yml --connector "twilio" --port 5002 --credentials credentials.yml --enable_api


  account_sid: "xxxxxxxxxxx"
  auth_token: "xxxxxxxxxxx"
  twilio_number: "+xxxxxx"

Resolved, there was a problem with the parsing credentials_file.
You need to edit the _create_external_channels method