In the “doc” gerritt project if you check the file docs\release\releaserepos.rst, you will see on line 95 it has following
dmaap data router (DR) <../submodules/dmaap/datarouter.git/docs/data-router/release-notes.rst>
This was correct in Casablanca, but in Dublin and master branch it seems the DR folder structure has changed to remove the data-router folder. So to match that, the link above should change to:
dmaap data router (DR) <../submodules/dmaap/datarouter.git/docs/release-notes.rst>

Please make that update in Dublin and cherry pick to master