我按照本指南尝试安装Ruby on Rails：http://elinux.org/RPi_Ruby_on_Rails
到达命令
curl -L get.rvm.io | bash -s stable --rails
我收到了消息
RROR: Could not find a valid gem 'rails' (>= 0), here is why:
Unable to download data from http://rubygems.org/ - no such name (http://rubygems.org/latest_specs.4.8.gz)
我该如何解决这个问题？