1、更新gem：sudo gem update --system
先要查看下源，如果源被墙了就换地址：https://gems.ruby-china.com
1.1、删除gem源：gem sources --remove https://gems.ruby-china.org/
1.2、修改gem源：gem sources -a https://gems.ruby-china.com
2、升级cocoapods：sudo gem install -n /usr/local/bin cocoapods --pre
