**Reason**:
The `PubSubHubbub` extension has been developed by two students in 2014 ([[ https://gerrit.wikimedia.org/r/#/q/owner:alexander.lehmann%2540student.hpi.uni-potsdam.de+status:merged | Alexander Lehmann ]] and [[ https://gerrit.wikimedia.org/r/#/q/owner:sebastian.brueckner%2540student.hpi.uni-potsdam.de+status:merged | Sebastian.Brueckner ]]).
The intent was to create an internal push notification system, but it never get used in our architecture. We nowadays have [[https://www.mediawiki.org/wiki/Change_propagation | change propagation]] which I guess would cover the need.
Anyway, @Lydia_Pintscher on T48525#1044776 explains how the extension is no more being worked on.
So I guess we should archive it. It can always be restored later on.
- [x] Archive documentation on `mediawiki.org` ( https://www.mediawiki.org/wiki/Extension:PubSubHubbub )
- [ ] Remove from `mediawiki/extensions` / `mediawiki/skins` ( along with in `.gitmodules`)
- [x] Remove tests in `integration/config` ( `zuul/layout.yaml` )
- [ ] Remove from `translatewiki` ( `groups/MediaWiki/mediawiki-extensions.txt` )
- [ ] Empty repository and add a OBSOLETE file.
- [x] Archive Phabricator project #MediaWiki-extensions-PubSubHubbub
- [x] Edit Phabricator project #MediaWiki-extensions-PubSubHubbub description for associated extension/skin with a link to this ticket
- [ ] Archive the extension's diffusion repository: rEPSH
- [ ] Mark the repository read-only in Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/PubSubHubbub
- [ ] Delete the GitHub mirror: http://github.com/wikimedia/mediawiki-extensions-PubSubHubbub