~$ ls /etc/apt/sources.list.d micahflee-ubuntu-ppa-xenial.list
It seems to be regignised, but after a an 'apt update' I still get ~$ apt search torbrowser-launcher Sorting... Done Full Text Search... Done torbrowser-launcher/flidas,now 0.2.4-1 amd64 [installed] helps download and run the Tor Browser Bundle