I tried to installed this n my debian machine, but I got stuck on the forst step. I cannot add the repository to my sources list.
I get this error message : (freely translated from my native language)
W: GPG error: http://www.debian-multimedia.org testing Release: Following signatures could not be verified because the open keys is not available: NO_PUBKEY 07DC563D1F41B907

Have tried all the repos with same result
any ideas?