The instance lists on wikitech's Special:NovaInstance stopped listing any of my instances, making it impossible to manage them such as adding puppet roles for MediaWiki-Vagrant.
Per Yuvi's suggestion, I logged out of wikitech and logged back in, and it magically began to work again. This is a bug that should probably be avoided, or else the error condition should be detected and an error message displayed instead of just showing no instances.
I can't figure out how to add puppet roles to a labs instance anymore, such as setting up the mediawiki-vagrant role on a new instance for server-side wiki testing.
The instance lists on wikitech no longer show any of my instances, so I cannot edit them there, where I used to add roles.
And I can't find any way to add puppet roles to an instance on horizon, which seems to be the new thing replacing the labs interfaces on wikitech.
If this is simply no longer available, then need a documentation update explaining what to do instead...