Comment 3 for bug 1060900

Ahh, if it is d-i doing it directly, so be it. The reason it should be separated out into a .d entry is basically, splitting out into .d entries are generally more manageable than using a main config file, especially if you want to undo this functionality change. (Remove the .d file rather than grepping through apt.conf trying to remove that line without blowing away other potential functionality in there.)

In our specific case, we don't want the running node to be using MAAS's local squid-deb-proxy setup, due to needing to add non-standard apt sources as part of a deployed Juju charm, and having a "local" archive mirror anyway. Ideally it would be best to have an option to not use a proxy server in MAAS (and there are bugs open asking for this), but failing that, I've added code to our charm to disable the apt proxy as one of the first steps of the charm, before the other apt sources are added. That is how I found the conf option is being put directly in /etc/apt/apt.conf, rather than an apt.conf.d file.