How to add request error handler

I'm trying to solve a problem that happens when a user has a notebook opened but JavaScript requests are failing. This happens because all requests are going through an authenticator. More info can be found here https://github.com/jupyterhub/jupyterhub/issues/2199.

Is it possible to add an error handler for when requests fail?

Start by reading the linked jupyterhub/jupyterhub issue #2199 and reproducing the notebook scenario where authenticated JavaScript requests fail. Then locate the notebook frontend request path and determine the expected error-handler behavior; the issue does not name a file, test, or precise completion criteria.

Written by the indexing model from the issue text.