No priority (or zero) specified for pin
This error appears always when I try to install or uninstall any package:
sudo apt-get remove lynx
Reading package lists... Done
E: No priority (or zero) specified for pin
Solution 1:
From the comments above, there is a file of ubuntu-esm-infra-trusty in the /etc/apt/preferences.d/ folder that contains a pin with no value on its priority. This file is for Ubuntu 14.04 Trusty ESM, but since you are running Ubuntu 16.04 LTS this file is not needed. Remove the file and you should be fine.