CDN: trunk URL couldn't be downloaded: https://raw.githubusercontent.com/CocoaPods/Specs/master/Specs/a/e/a/Flipper/0.37.0/Flipper.podspec.json, error: Failed to open TCP connection to raw.githubusercontent.com:443 (Connection refused - connect(2) for "raw.githubusercontent.com" port 443)
在podfile文件中添加source源：
source 'https://github.com/CocoaPods/Specs.git'
删除cdn源：（CocoaPods到1.8.4，国内cdn源用不了）
#source 'https://cdn.cocoapods.org/'
pod repo remove trunk
pod install
