homebrew报错Error: unknown or unsupported macOS version: :mountain_lion问题解决

homebrew是mac平台下非常方便的包管理工具。

用brew install xxx 命令时出现报错提示：

Error: unknown or unsupported macOS version: :mountain_lion

这时用brew doctor命令进行检查，其中出现：

Warning: Some installed kegs have no formulae!
This means they were either deleted or installed with `brew diy`.
You should find replacements for the following formulae:
  python@2
  mongodb

这时需要将python@2,mongodb这两个包删除：

brew uninstall python@2 mongodb

接下来就可以顺利地用brew install xxx 命令安装需要的各种包，问题解决！