直接執行sudo gem install cocoapods，會報錯， ERROR: While executing gem ... (Errno::EPERM) Operation not permitted - /usr/bin/pod
替換成：sudo gem install -n /usr/local/bin cocoapods
然后又報錯
WARNING: Unable to pull data from 'http://ruby.taobao.org/': bad response Not Found 404 (http://ruby.taobao.org/specs.4.8.gz)
網上查才知道taobao鏡像已經改成https的了。
所以解決方案如下：
1、替換為淘寶鏡像，注意是https
gem sources -a https://ruby.taobao.org/
2、執行以下命令
sudo gem install -n /usr/local/bin cocoapods
