执行 pod lib lint 时，报错：

ERROR | [iOS] unknown: Encountered an unknown error (Could not find a `ios` simulator (valid values: com.apple.coresimulator.simruntime.ios-10-3, com.apple.coresimulator.simruntime.ios-12-1, com.apple.coresimulator.simruntime.ios-8-1, com.apple.coresimulator.simruntime.tvos-12-1, com.apple.coresimulator.simruntime.watchos-5-1). Ensure that Xcode -> Window -> Devices has at least one `ios` simulator listed or otherwise add one.

 原因rubygem源发生变化

 https://gems.ruby-china.org/ 域名不可用 要换成 https://gems.ruby-china.com/

移除旧源添加新的ruby源

gem sources --add https://gems.ruby-china.com/ --remove https://gems.ruby-china.org/

查看ruby源是否替换成功

gem sources -l

如果替换成功，重新初始化cocoapods

sudo gem install cocoapods

pod lib lint xxx.podspec 验证出错 Could not find a `ios` simulator