Error fetching https://ruby.taobao.org/:bad response Not Found 404 (https://gems.ruby-china.org/...

安装gem镜像源为淘宝镜像源失败的时候失败

错误信息：

C:\Users\Administrator>gem sources -a https://ruby.taobao.org/
Error fetching https://ruby.taobao.org/:
        bad response Not Found 404 (https://gems.ruby-china.org/specs.4.8.gz)

解决方法：
将gem sources -a https://ruby.taobao.org/
改成gem sources -a http://gems.ruby-china.com/

就可以了

原因：