Error I was getting:
...
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 14E4942973C62A1B


Tried:

leopardus@felis:~$ apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 14E4942973C62A1B
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /tmp/tmp.v8i9dd8YMe --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyring /etc/apt/trusted.gpg.d//steam.gpg --recv-keys --keyserver keyserver.ubuntu.com 14E4942973C62A1B
gpg: requesting key 73C62A1B from hkp server keyserver.ubuntu.com
gpg: no writable keyring found: eof
gpg: error reading `[stream]': general error
gpg: Total number processed: 0


?!