macOS安装homebrew cask 问题&解决办法

命令行：$ brew install brew-cask-completion

报错：

brew cask install caskroom/cask/brew-cask 

Error: Cask 'brew-cask' is unavailable: '/usr/local/Homebrew/Library/Taps/caskroom/homebrew-cask/Casks/brew-cask.rb' does not exist. 

解决办法：

$ brew install brew-cask-completion

Downloading https://github.com/xyb/homebrew-cask-completion/archive/v2.1.tar

==> Downloading from https://codeload.github.com/xyb/homebrew-cask-completion/ta

######################################################################## 100.0%

==> Caveats

Bash completion has been installed to:

  /usr/local/etc/bash_completion.d

==> Summary