:~$ do-release-upgrade 
Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife

Get:1 Upgrade tool signature [819 B]                                           
Get:2 Upgrade tool [1,253 kB]                                                  
Fetched 1,254 kB in 6s (149 kB/s)                                              
authenticate 'xenial.tar.gz' against 'xenial.tar.gz.gpg' 
extracting 'xenial.tar.gz'

Reading cache

Checking package manager

Can not upgrade 

An upgrade from 'vivid' to 'xenial' is not supported with this tool.