Adding Ubuntu PPA repository behind a firewall. When you are behind a corporate firewall that only allows outbound traffic on ports 80 and 433 the usual apt-add-repository command will not work. To get around it. Here is the workaround.

gistfile1.tcsh

# trying to install PPA behind firewall fails:
$ sudo add-apt-repository ppa:chris-lea/node.js
  gpg: requesting key C7917B12 from hkp server keyserver.ubuntu.com
  gpgkeys: HTTP fetch error 7: couldn't connect to host
  gpg: no valid OpenPGP data found.
  gpg: Total number processed: 0
  recv failed

# this is how you get around it (use the key from the command above)
$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys C7917B12