It isn't my project but OAuthlib needs some help, including Flask-OAuthlib. The contributors there are slow to respond to open issues. OAuthlib is trying to make OAuth1 and OAuth2 easier to implement but the contributors get in the way of accomplishing this when they don't respond promptly to issues.
OAuthlib: https://github.com/idan/oauthlib
Flask-OAuthlib: https://github.com/lepture/flask-oauthlib
Requests-OAuthlib: https://github.com/requests/requests-oauthlib