"Launchpad-getkeys is a script that imports these missing keys
When adding PPAs to Ubuntu via "apt-add-repository" the PPA and
its key will be imported. These GPG keys are a way to verify the
packages in that PPA. But if you add a PPA when the Ubuntu key
server is down the key will not be imported and the PPA will
produce an error every time you try refreshing your packages.
Ubuntu Forums user (blackgr) created a script called
launchpad-getkeys that will import all missing keys