**Reason**
Not used, never used, and won't be used in the future
**To-do list**
- This task
-- [x] Add maintainers of that extension/skin as subscribers to this task (if they have no apparent Phabricator account, notify them on-wiki or via email if possible and note it here).
- Configuration/tests/integrations/etc.
-- ~~Remove from `mediawiki/extensions` / `mediawiki/skins` (along with in `.gitmodules`).~~ Not a extension/skin
-- [x] Remove tests in [[ https://gerrit.wikimedia.org/g/integration/config | integration/config ]] (`zuul/layout.yaml`).
-- ~~Remove manifest/other references from `mediawiki/vagrant` if they exist.~~ Do not exist.
-- ~~Remove from https://doc.wikimedia.org/cover-extensions/ if present (requires #continuous-integration-infrastructure shell user to delete directly from the server).~~ None found.
- Repositories
-- [x] Empty repository leaving only the README indicating the repo is archived and referring to this task by URL.
-- [x] Mark the repository read-only in Gerrit.
-- [ ] Archive the diffusion repository.
-- [ ] Delete the GitHub mirror: https://github.com/wikimedia/mediawiki-libs-etcd