The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5BA31D57EF5975CA
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://pkg.jenkins.io/debian-stable binary/ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5BA31D57EF5975CA
W: Failed to fetch https://pkg.jenkins.io/debian-stable/binary/Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5BA31D57EF5975CA
W: Some index files failed to download. They have been ignored, or old ones used instead.