Broken link.
Topic on Extension talk:DiscussionTools
Which link is broken where?
"The requested project does not exist"
The link on https://www.mediawiki.org/wiki/Extension:DiscussionTools with the text README.md that points to https://phabricator.wikimedia.org//r/p/mediawiki/extensions/DiscussionTools;browse/master/README.md .
Oh, right, yeah, that's a bug with Template:Git file. You should report that there.
Turns out I've already complained about this two years ago: Topic:Ufsi1mmwoxghtkyd. :-)