after running sudo apt update
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04 Release: The following signatures were invalid: KEYEXPIRED 1501595774
W: Failed to fetch http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04/Release.gpg The following signatures were invalid: KEYEXPIRED 1501595774
How can I download the correct key?