常见问题
0. 找不到指定版本的XXX
[!] CocoaPods could not find compatible versions for pod “XXX”:
1. 找不到指定依赖
None of your spec sources contain a spec satisfying the dependency:
You have either:
* out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
* mistyped the name or version.
* not added the source repo that hosts the Podspec to your Podfile.
2. 连接不到服务器
[!] CDN: trunk URL couldn't be downloaded: https://cdn.cocoapods.org/all_pods_versions_f_2_b.txt Response: Couldn't connect to server
3. 验证失败
[!] CDN: trunk URL couldn't be downloaded: https://cdn.cocoapods.org/deprecated_podspecs.txt Response: SSL peer certificate or SSH remote key was not OK
Trunk源总有问题，导致不能install，不能update，不能search
官方解释
https://blog.cocoapods.org/CocoaPods-1.8.0-beta/
大概就是这么个意思
CocoaPods 1.8 切换CDN作为默认的spec repo源，并附带了一些增强功能！
在1.8版本中，CocoaPods不再需要克隆现在庞大的master specs repo才能正常工作，用户几乎可以立即将他们的项目与CocoaPods集成，支持master增量下载。
查看pod版本
pod --version,更新到1.8之后的版本
最终解决
0. 在Podfile最上面添加指定master源
source 'https://github.com/CocoaPods/Specs.git'
1. 移除trunk源
pod repo remove trunk
Install, update, search,世界又变得美好