After apt-get update a warning is thrown : "W: There is no public key available for the following key IDs: AA8E81B4331F7F50"

[nfacciolo]

Following https://github.com/openvlc/OpenVLC/blob/master/OpenVLC1.3_revA/README.md

After executing sudo apt-get update The following warning is thrown. W: There is no public key available for the following key IDs: AA8E81B4331F7F50

It could be great the key was added in the given image