brew services 报错：Error: uninitialized constant Homebrew::Service::System
brew services status xxx
报错：
Error: uninitialized constant Homebrew::Service::System
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-services/cmd/services.rb:61:in `services'
/usr/local/Homebrew/Library/Homebrew/brew.rb:94:in `<main>'
这个错误提示说是 Homebrew::Service::System 没有被初始化，可能是 homebrew-services 没有正确安装或者安装过程中出了问题。可以尝试重新安装 homebrew-services，方法如下：
卸载 homebrew-services
brew uninstall homebrew/services
重新安装 homebrew-services
brew tap homebrew/services
brew install homebrew/services
若安装不成功，可以再次执行
brew update
brew upgrade
rm -rf /usr/local/Homebrew/Library/Taps/homebrew/homebrew-services
brew services
brew services 项目：https://github.com/Homebrew/homebrew-services