I noticed that certain links to the Astropy documentation, which recently worked, are now broken:

• https://docs.astropy.org/en/stable/development/testguide.html
• https://docs.astropy.org/en/stable/development/codeguide.html
• https://docs.astropy.org/en/stable/testhelpers.html

We use some of those links in the documentation of our own repo's, e.g. here: https://measure-extinction.readthedocs.io/en/latest/

Updating them to "latest" instead of "stable" fixed our problem, but I thought I should put an issue in anyway (as @eteq suggested).