这个问题可能由于MacOS从10.11升级到10.12所导致,运行brew命令会提示如下错误:

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- mach (LoadError)

首先打开终端进入 /usr/local路径,如果你的brew不是按照在如上路径,则进入如下目录:

cd `brew --prefix`

运行git status命令,如果Homebrew是dirty的,则运行如下命令:

git reset --hard && git clean -df

然后运行如下两个命令:

brew doctor
brew update

然后brew会提示你因为用的是10.12运行时会报如下警告:

Formula file is modified!

所以需要安装以下几个包:

brew install gtk-mac-integration libepoxy py2cairo pygobject pygtk

我是做到这一步就ok了,如果brew还报错误,你可以尝试如下两条命令:

$ sudo rm /System/Library/Frameworks/Ruby.framework/Versions/Current
$ sudo ln -s /System/Library/Frameworks/Ruby.framework/Versions/1.8 /System/Library/Frameworks/Ruby.framework/Versions/Current

good luck!