brew link python3出错

brew安装Python3时出现的问题：

$ brew install python3
Warning: python3 3.6.3 is already installed, it's just not linked.
You can use `brew link python3` to link this version.
$ brew link python3
Linking /usr/local/Cellar/python3/3.6.3... Error: Permission denied @ dir_s_mkdir - /usr/local/Frameworks
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发现/usr/local/下没有路径/usr/local/Frameworks
需要新建该路径，并修改权限

解决：

$ sudo mkdir /usr/local/Frameworks
$ sudo chown $(whoami):admin /usr/local/Frameworks
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成功：

$ brew link python3
Linking /usr/local/Cellar/python3/3.6.3... 1 symlinks created
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参考：
https://github.com/Homebrew/homebrew-core/issues/19286