I have an /etc/apt/sources.list.d file with the line
deb https://download.01.org/gfx/ubuntu/16.04/main wily main #Intel Graphics drivers
Now, when I try to apt-get upgrade, I get a message saying:
W: GPG error: https://download.01.org/gfx/ubuntu/16.04/main wily InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2CC2A1B90A3B3268
Why is the repository not signed? What can I do about it?
