[!] Unable to add a source with url `https://github.com/CocoaPods/Specs.git` named `master-1`.

pod install 报错
[!] Unable to add a source with url https://github.com/CocoaPods/Specs.git named master-1.
You can try adding it manually in ~/.cocoapods/repos or via pod repo add.

可能原因是xcode不止一个.
解决方法
sudo xcode-select -switch /Applications/Xcode.app
sudo xcode-select -switch 后边加xcode地址
然后再执行pod install.即可.