In 60239bd637 the assumption that init_oidc_client could be imported
from oidc_handler was introduced into admin_routes.py.
However, init_oidc_client was defined in __init__.py, leaving us with
the options of:
1. Importing from .
2. Moving the implementation to oidc_handler, and importing in
__init__.py
I've gone with option 2.
88b02bbdc2