Edite seu sources.list
da seguinte forma:
deb http://old-releases.ubuntu.com/ubuntu/ yakkety main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ yakkety-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ yakkety-security main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ yakkety-backports main restricted universe multiverse
Salvar e atualizar:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install gawk