Customize "Proxy server is refusing connections" error screen

💡 Proposal

We've discussed this idea briefly with @ebanam during the last UX Team meeting. It's also something that we've felt the need for at Tails in the past: https://gitlab.tails.boum.org/tails/tails/-/issues/8061.

User Story

My understanding is that the "Proxy server is refusing connections" error screen appears when Tor Browser cannot connect to the Tor client for some reason.

It seems that this error case happened many times in the past and is still a hop topic right now.

Ideally, all these errors should not happen in the first place, but, when they do, I think that this error screen could be much more helpful.

Usability Heuristics #9 makes error messages an integral part of usability and recommends that:

Error messages should be expressed in plain language (no error codes), precisely indicate the problem, and constructively suggest a solution.

For example, right now it's talking about a "proxy server" and not explaining clearly that the problem is about the Tor client. The suggested solutions are not helpful either.

Security and Privacy Implications

Security

Privacy

Accessibility Implications

Other Trade-Offs

Prior Art

Does this feature exist in other browsers?

Yes
- Firefox

The screen is well designed for Firefox, pointing to practical solutions. But it's very misleading in the context of Tor Browser.