Ubuntu 16.10 reaches end of life
Ubuntu 16.10 "Yakkety Yak" arrived back in October last year. Since then, the nine-month support period offered to non-LTS releases has passed, and so this Linux version has just become obsolete and it will no longer receive updates.
According to the official email recently sent less than a day ago by Ubuntu Release Team member Adam Conrad, "as of today (July 20, 2017), Ubuntu 16.10 is no longer supported. No more package updates will be accepted to 16.10, and it will be archived to old-releases.ubuntu.com in the coming weeks."
Since Ubuntu 17.04 "Zesty Zapus" has been around for a few months already, upgrading to it is not a choice, but a must. Doing so, the user would get support until January 2018. On the other hand, some might want to choose Ubuntu 16.04 LTS instead, but that would require them to reinstall the system instead of upgrading.