bullseye-backports - docbook-slides-demo
The Vcs-* headers in the last upload of this package are still pointing to alioth (svn://svn.debian.org/debian-xml-sgml/packages/docbook-slides-demo/trunk/) . However, Alioth has been turned off and its repositories are no longer directly accessible.
Please migrate the package to alioth's replacement, salsa and update the Vcs-* headers.