Updates for EOL Ubuntu releases

When release reaches it's EOL, the repositories are no longer available at old location, so we have to change their addresses like this:

Edit /etc/apt/sources.list and change 'archive.ubuntu.com' to 'old-releases.ubuntu.com'

or

We can do this with 

sudo sed -i -e 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

and then update with 

sudo apt-get update && sudo apt-get dist-upgrade

Thanks to fossfreedom for providing the info on this topic.