GooglePlusAuth backend do not store 'access_token' on extra_data (psa v0.1.17)

[jgsogo]

(working with python-social-auth v0.1.17)

I'm working on a project with facebook, twitter and g+ backends and I have found an issue with g+.

GooglePlusAuth backend stores 'code' on extra_data, but as it is said on [1] this code is for only one-time use and should be exchanged for an access_token. I expect PSA to do this step.

I'm trying to figure out how to solve this issue but I'm a little bit confused about the oauth2 thing; I'll update this issue if I manage to solve it.

Thanks.

NOTE.- Related to this, when the user disconnect g+ there is an unexpected behaviour because 'access_token' is not found at [2] and tokens are not removed.

[1] https://developers.google.com/+/web/signin/server-side-flow#step_6_send_the_authorization_code_to_the_server

[2] https://github.com/omab/python-social-auth/blob/v0.1.17/social/pipeline/disconnect.py#L23

[omab]

Thanks!