A few things happening here:

The website has updated 4xx and 5xx pages we can copy. I would also like to redo some pages with more personality at some point though, but this is a later problem.
There are multiple versions of the 404 page, and some features we might want to bring forward into the new dashboard.
The new dashboard loads a number of assets and one of the things I expect to hit is the bug where the URLs and assets aren't defined on the instance that is serving the 404 page. We have a few bugs here in the past, and it's one of the reasons our error pages are more empty now.
But a large looming issue is that the error pages we show are going to be more heavily branded like our application, which is an odd fit for user documentation sites. Our CAS/etc login for documentation views should be super minimal. This is a later problem, but defining it for now.
🆕 Show a log in form on the commercial 404 page. See:
- https://github.com/readthedocs/readthedocs-corporate/issues/1760

Work here

[x] Application error pages
- [x] 404 page
- [x] 404 page login conditional for commercial
- [x] 500 page
- [x] 403 page
[x] #304
- Calling this separate work to deal with later.

readthedocs / ext-theme