更新时，我收到以下消息：
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://mirrors.evowise.com/linuxmint/packages tricia Release: The following signatures were invalid: BADSIG A6616109451BBBF2 Linux Mint Repository Signing Key <root@linuxmint.com>
W: Failed to fetch http://mirrors.evowise.com/linuxmint/packages/dists/tricia/Release.gpg The following signatures were invalid: BADSIG A6616109451BBBF2 Linux Mint Repository Signing Key <root@linuxmint.com>
W: Some index files failed to download. They have been ignored, or old ones used instead.
我使用的是Linux Mint 19.3（基于Ubuntu 18.04）。这是在我尝试使用当前发行版尝试将Kubuntu 20.04安装为双启动后发生的，但是由于启动/ grub问题而失败。
