cocoapods找不到第三方库 [!] Unable to find a pod with name, author, summary, or description matching AFNetworking
方法一：
删除cocoapods的索引，然后重新search
rm ~/Library/Caches/CocoaPods/search_index.json
pod search AFNetworking
出现
Creating search index for spec repo 'master'.. Done!
会触发cocoapods重新拉这个索引文件，完成
方法二：
重新安装cocoapods