You got a wrong PPA url.
It's "ppa:tualatrix/ppa", not "ppa:tualatrix/ubuntu-tweak"
Try
sudo add-apt-repository ppa:tualatrix/ppa
You got a wrong PPA url.
It's "ppa:tualatrix/ ppa", not "ppa:tualatrix/ ubuntu- tweak"
Try
sudo add-apt-repository ppa:tualatrix/ppa