Mac 下安装pip
在mac 10.12.6版本下brew install pip 安装失败：
报错：
Error: No available formula with the name "pip" Homebrew provides pip via: `brew install python`. However you will then have two Pythons installed on your Mac, so alternatively you can install pip via the instructions at: https://pip.readthedocs.io/en/stable/installing/
解决方法：
sudo easy_install pip