Comment 3 for bug 1020995

Sorry? Don't set it to duplicate because that bugs have a different nature. apt-file is a frontend tool which sneaks information from apt's configuration making blind assumptions about its interface. apt-cacher-ng is middle-layer.

The origin of this bug is IMHO the failure to retrieve the mirrors.txt file because it's not in the list of valid file names. Ubuntu maintainer could just add it to volatile file patterns in acng_defaults.cc and that should be enough to fix it.