Update mozilla-django-oidc to 0.6.0
Update mozilla-django-oidc to 0.6.0

This picks up the fix for infinite redirect on login when the OIDC OP
returns an error, but the Django session is still valid thus causing
the user to enter a nether-void between two realities from which they
can't escape except by tossing their cookies.

Fixes #412

mozilla/standup,mozilla/standup,mozilla/standup,mozilla/standup