According to https://bugs.launchpad.net/ubuntu/+source/apt-file/+bug/220396/comments/3 some mirrors drop the Contents-*.gz files in order to save space. But the Contents-*.gz files seem to be missing on the master servers, too.
According to https:/ /bugs.launchpad .net/ubuntu/ +source/ apt-file/ +bug/220396/ comments/ 3 some mirrors drop the Contents-*.gz files in order to save space. But the Contents-*.gz files seem to be missing on the master servers, too.