2019-07-25：
Error fetching https://gems.ruby-china.org/:
bad response Not Found 404 (https://gems.ruby-china.org/specs.4.8.gz)
原因是 ruby-china 更换了域名
https://gems.ruby-china.com
命令替换为 gem sources --add https://gems.ruby-china.com 解决
-bash: /usr/local/bin/pod: /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby: bad interpreter: No such file or directory
操作：
1、更新gem：sudo gem update --system
2、删除gem源：gem sources --remove https://ruby.taobao.org/
3、修改gem源：gem sources -a https://gems.ruby-china.org
4、查看gem源是否是最新的：gem sources -l
5、升级cocoapods：sudo gem install -n /usr/local/bin cocoapods --pre
6、查看升级后的cocoapods版本：pod --version