Issue with App Authentication

[MD-CO]

I'm attempting to authenticate my app via python, as instructed here: https://github.com/debrouwere/facebook-insights

`import facebookinsights as fi

this will launch a web browser to authenticate

pages = fi.authenticate(
client_id='your client id',
client_secret='your client secret',
)`

Whenever I attempt this, the browser opens up, asks me to authenticate, and I get the following message in my browser: 'Authentication flow completed. You may close the browser tab.'

However, in the actual python shell, I get the following error:
in process_token_request
raise KeyError(PROCESS_TOKEN_ERROR.format(key=bad_key, raw=r.content))
KeyError: 'Decoder failed to handle access_token with data as returned by provider. A different decoder may be needed. Provider returned: {"access_token":"[MY_ACCESS_TOKEN]","token_type":"bearer","expires_in":5183998}'

Not sure what the root of this issue is.