https://mirrors.ustc.edu.cn/rubygems/
Rubygems 仓库镜像
gem sources #列出默认源
gem sources --remove https://rubygems.org/ #移除默认源
gem sources -a https://mirrors.ustc.edu.cn/rubygems/ #添加科大源
参考: Gem Source Mirrors @ Bundle Docs
bundle config mirror.https://rubygems.org https://mirrors.ustc.edu.cn/rubygems/