CDN: trunk Repo update failed

CDN: trunk URL couldn't be downloaded: https://raw.githubusercontent.com/CocoaPods/Specs/master/Specs/c/5/2/JKCategories/1.0/JKCategories.podspec.json, error: Failed to open TCP connection to raw.githubusercontent.com:443 (Connection refused - connect(2) for "raw.githubusercontent.com" port 443)

解决方案
在 Podfile 中加上 source "https://github.com/CocoaPods/Specs.git", 就不会使用 CDN