Delete the auth token when logging out.

Before this, authentication tokens were kept in the database, even when
someone logged out. This is unwanted behaviour, as logging in will create
yet another token anyway there is no reason to keep the token around.

pillar/api/blender_cloud/subscription.py

@@ -83,13 +83,19 @@ def update_subscription():
     """
 
     import pprint
+    from pillar import auth
     from pillar.api import blender_id, service
     from pillar.api.utils import authentication
 
     my_log: logging.Logger = log.getChild('update_subscription')
     user_id = authentication.current_user_id()
 
-    bid_user = blender_id.fetch_blenderid_user()
+    try:
+        bid_user = blender_id.fetch_blenderid_user()
+    except blender_id.LogoutUser:
+        auth.logout_user()
+        return '', 204
+
     if not bid_user:
         my_log.warning('Logged in user %s has no BlenderID account! '
                        'Unable to update subscription status.', user_id)