How do I get rid of the NO_PUBKEY warning when updating from a PPA

If you've enabled a PPA in your local configuration (via software sources, synaptic or /etc/sources.list directly) when you update your packages you may get a warning that looks like this:

  W: GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 632D16BB0C713DA6

This message means you need to import the repository key into your local apt keyring. Details are at https://help.launchpad.net/Packaging/PPA/InstallingSoftware but the summary is that solving the problem above would just require issuing this command in your prompt:

  sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 632D16BB0C713DA6