Reason:
The DeepSea skin was originally created a long time ago, which was more or less a Vector skin with only some slight appearance changes (there used to be some functionality changes too, but no more). So I re-implemented it as a pure-CSS theme for Vector pretty recently, in https://gerrit.wikimedia.org/r/#/c/359623/
- Archive documentation on mediawiki.org - http://mediawiki.org/wiki/Skin:DeepSea
- Remove from mediawiki/skins + .gitmodules
- Remove tests in intregation/config ( zuul/layout.yaml )
- Remove from translatewiki ( groups/MediaWiki/mediawiki-skins.txt )
- Archive Phabricator project DeepSea for associated extension/skin
- Edit Phabricator project DeepSea description for associated extension/skin with a link to this ticket
- Archive the extension's diffusion repository: https://phabricator.wikimedia.org/r/project/mediawiki/skins/DeepSea
- Mark the repository read-only in Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/skins/DeepSea