我正在使用python37作为基础镜像制作项目镜像，但构建过程中执行apt-get update时出现GPG签名错误
本地操作系统为Mac OS，docker 环境为desktop for docker ：
Docker version 20.10.7, build f0df350
错误详情：
Err:1 http://ports.ubuntu.com/ubuntu-ports focal InRelease At least one invalid signature was encountered. Get:4 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease [107 kB] Err:2 http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease At least one invalid signature was encountered. Err:3 http://ports.ubuntu.com/ubuntu-ports focal-backports InRelease At least one invalid signature was encountered. Err:4 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease At least one invalid signature was encountered. Reading package lists... Done W: GPG error: http://ports.ubuntu.com/ubuntu-ports focal InRelease: At least one invalid signature was encountered. E: The repository 'http://ports.ubuntu.com/ubuntu-ports focal InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. W: GPG error: http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease: At least one invalid signature was encountered. E: The repository 'http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default.
解决方案：
docker image prune -a
会清理一些镜像，然后再进行构建，就没有报错了
参考文章：stackoverflow