pod install 时候遇到报错
[!] CDN: trunk Repo update failed - 113 error(s):
CDN: trunk URL couldn't be downloaded: https://cdn.jsdelivr.net/cocoa/Specs/1/1/7/SDWebImage/2.4/SDWebImage.podspec.json Response: Couldn't resolve host name
CDN: trunk URL couldn't be downloaded: https://cdn.jsdelivr.net/cocoa/Specs/1/1/7/SDWebImage/2.5/SDWebImage.podspec.json Response: Timeout was reached
CDN: trunk URL couldn't be downloaded: https://cdn.jsdelivr.net/cocoa/Specs/1/1/7/SDWebImage/2.7.4/SDWebImage.podspec.json Response: Couldn't connect to server
尝试解决问题：i
1.准备修改hosts
199.232.4.133 raw.githubusercontent.com
cd /etc
ls -a
rm -rf .hosts.swp //这个命令针对如果之前对host编辑却没有保存好数据的时候 同样在未保存界面编辑D删除也可以
sudo vim hosts
输入i 进入编辑状态（insert状态，如下图）
按esc 输入 :qw 退出 (这个hosts的编辑十分难用，编辑完一定要再查看。而且每次如果不保存好就关掉的话也会出问题)
移除之前的trunk， 在podfile中添加source 'https://github.com/CocoaPods/Specs.git'
pod repo remove trunk
经过以上处理后重新pod 解决了。
