sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com B0BE17C2A0C914F086B7B8327D2C7A23BF810CD5

Replace B0BE17C2A0C914F086B7B8327D2C7A23BF810CD5 with the fingerprint of the PPA key you’re dealing with.

(from Launchpad)