Comment 14 for bug 1697120

Um, apt-file in zesty is actually too old to trigger this, so I manually added the config file for testing it, and verified it that way:

root@d5c73dbb41a2:/# apt update
Hit:1 http://security.ubuntu.com/ubuntu zesty-security InRelease
Hit:2 http://archive.ubuntu.com/ubuntu zesty InRelease
Hit:3 http://archive.ubuntu.com/ubuntu zesty-updates InRelease
Hit:4 http://archive.ubuntu.com/ubuntu zesty-backports InRelease
Hit:5 http://archive.ubuntu.com/ubuntu zesty-proposed InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
7 packages can be upgraded. Run 'apt list --upgradable' to see them.
[...]
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:46
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:46
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:48
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:48
root@d5c73dbb41a2:/# apt install libapt-pkg5.0
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  libapt-pkg5.0
1 upgraded, 0 newly installed, 0 to remove and 6 not upgraded.
Need to get 784 kB of archives.
After this operation, 1024 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu zesty-proposed/main amd64 libapt-pkg5.0 amd64 1.4.8 [784 kB]
Fetched 784 kB in 0s (921 kB/s)
debconf: delaying package configuration, since apt-utils is not installed
(Reading database ... 6656 files and directories currently installed.)
Preparing to unpack .../libapt-pkg5.0_1.4.8_amd64.deb ...
Unpacking libapt-pkg5.0:amd64 (1.4.8) over (1.4.6~17.04.1) ...
Setting up libapt-pkg5.0:amd64 (1.4.8) ...
Processing triggers for libc-bin (2.24-9ubuntu2.2) ...
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list:14
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list:14
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list:24
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list:24
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:8 and /etc/apt/sources.list:16
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:8 and /etc/apt/sources.list:16
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:8 and /etc/apt/sources.list:26
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:8 and /etc/apt/sources.list:26
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:46
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:46
W: Target Contents-deb-legacy (Contents-amd64) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:48
W: Target Contents-deb-legacy (Contents-all) is configured multiple times in /etc/apt/sources.list:44 and /etc/apt/sources.list:48
root@d5c73dbb41a2:/# apt update
Hit:1 http://security.ubuntu.com/ubuntu zesty-security InRelease
Hit:2 http://archive.ubuntu.com/ubuntu zesty InRelease
Hit:3 http://archive.ubuntu.com/ubuntu zesty-updates InRelease
Hit:4 http://archive.ubuntu.com/ubuntu zesty-backports InRelease
Hit:5 http://archive.ubuntu.com/ubuntu zesty-proposed InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
6 packages can be upgraded. Run 'apt list --upgradable' to see them.