运行命令brew install pip3，结果界面一直卡在Updating Homebrew...上，有两种解决办法
方法一：直接关闭brew每次执行命令时的自动更新（推荐）
vim ~/.bash_profile
# 新增一行
export HOMEBREW_NO_AUTO_UPDATE=true
方法二：替换brew源
cd "$(brew --repo)"
git remote set-url origin https://mirrors.ustc.edu.cn/brew.git
#替换homebrew-core.git
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git
brew update
# 备用地址-1
cd "$(brew --repo)"
git remote set-url origin https://git.coding.net/homebrew/homebrew.git
brew update
# 备用地址-2
cd "$(brew --repo)"
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/brew.git
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew-core.git
brew update
如果备用地址都不行，那就只能再换回官方地址了
#重置brew.git
cd "$(brew --repo)"
git remote set-url origin https://github.com/Homebrew/brew.git
#重置homebrew-core.git
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://github.com/Homebrew/homebrew-core.git
