When the body is encoded, a mix of bytes and unicode happens and it
fails at this line

https://github.com/requests/requests-oauthlib/blob/c472e6bf0468f1bd52b70a64e9aac92bee41c491/requests_oauthlib/oauth2_session.py#L285

(Pdb) body
u'grant_type=refresh_token&allow_redirects=True&refresh_token=b%27z9BSRKqf2QD4pcDhqj%27&client_id=CLIENT_ID&client_secret=CLIENT_SECRET'

(note those weird `%27` in the string)

`paginate` method is shared between both services and each service
implement `get_next_url_to_paginate` and `get_paginated_results`.