An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://dl.winehq.org/wine-builds/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672FFailed to fetch https://dl.winehq.org/wine-builds/ubuntu/dists/xenial/InRelease  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672FSome index files failed to download. They have been ignored, or old ones used instead.