If like me you have had annoying 404's pop up during
apt-get update and no amount of fiddling with the
/etc/apt/source.list then it means your Ubuntu has reached End of Life. AKA: it's an OAP.
It needs a bus pass.
So to help it out simply change all instances of
old-releases . Like so:
sudo apt-get update to get the 'fresh' list of packages you're used to But its highly recommended you upgrade your distro to a more up-to-date version by following the steps at Ubuntu's community EOL page.