Upon trying to impersonate a user to debug T265449 I got a 403 error. The logs read:
OAuth POST from https://hub.paws.wmcloud.org/hub/api/oauth2/authorize?client_id=jupyterhub-user-Ptj&redirect_uri=%2Fuser%2FPtj%2Foauth_callback&response_type=code&state=[SECRET] != http://hub.paws.wmcloud.org/hub/api/oauth2/authorize?client_id=jupyterhub-user-Ptj&redirect_uri=%2Fuser%2FPtj%2Foauth_callback&response_type=code&state=[SECRET] [W 2020-10-14 11:31:24.890 JupyterHub web:1786] 403 POST /hub/api/oauth2/authorize?client_id=jupyterhub-user-Ptj&redirect_uri=%2Fuser%2FPtj%2Foauth_callback&response_type=code&state=[SECRET]
The issue seems to be http vs https.