base64.encodestring was deprecated and removed in Python 3.9 . Use encodebytes instead.

[tirkarthi]

https://github.com/omab/python-social-auth/blob/81c0a542d158772bd3486d31834c10af5d5f08b0/social/tests/models.py#L169

https://docs.python.org/3/library/base64.html#base64.encodestring