Would this show up in the status bar or in the developer console? This is probably a thing that we would want to have a test for. I am short on time a few days more but otherwise happy to help with writing the robot test for it.

Would this show up in the status bar or in the developer console?

In the developer console

Our console output is noisy to the point of being useless... if this is a big problem, should we see about integrating with the in-UI log output?

should we see about integrating with the in-UI log output?

That would be a big improvement for people who don't know how to open the dev tools (most JupyterLab users I guess), so they get an idea why it does not work.

I just got bitten by this error when opening .gitignore file, for me it was leading to:

TypeError: Cannot read property 'replace' of null
    at url.js:61
    at Array.map (<anonymous>)
    at Object.join (url.js:61)
    at Function.solve_uris (connection_manager.ts:335)
    at DocumentConnectionManager.connect_socket (connection_manager.ts:131)
    at DocumentConnectionManager.connect (connection_manager.ts:282)
    at FileEditorAdapter.connect (adapter.ts:490)
    at FileEditorAdapter.connect_document (adapter.ts:324)
    at new FileEditorAdapter (file_editor.ts:55)
    at WidgetAdapterManager.connectWidget (adapter_manager.ts:66)

Anyways, merging as is and I will iterate to add some indication of this in the UI.

Thank you @martinRenou!