gem install compass

如果安装不了，更换源试试

先移出

gem sources --remove https://rubygems.org/

再添加

gem source -a http://gems.ruby-china.com

然后再重新运行，就可以愉快的安装了。

gem install compass

如果遇到
You don't have write permissions for the /Library/Ruby/Gems/2.6.0 directory. 可以点此查看