Comment 0 for bug 1821251

Disco's apt started downloading cnf (command-not-found) files but debmirror does not download these files, so when pointing a disco machine at a mirrored archive, apt-get update errors. Eg, we need to mirror the Commands-*.xz files: http://archive.ubuntu.com/ubuntu/dists/disco/main/cnf/

The fix is straightforward since the files are quite similar to dep11, and debmirror already handles dep11. Here is a patch that simply copy/pastes the various dep11 code. It is lightly tested and appears to do the job.