刚在阿里云的服务器上升级 ruby 版本，然后安装 gem 时出现错误

ERROR:  While executing gem ... (Gem::RemoteFetcher::FetchError)
    bad response Bad Gateway 502 (https://cdn.gems.ruby-china.org/quick/Marshal.4.8/bundler-1.11.2.gemspec.rz)

cdn 服务出现请求错误。