railsのスクレイピングで(SocketError)

前提・実現したいこと

railsでスクレイピングの練習をしています。
模範のソースコードをコピーしたのですがerrorがでます。
Temporary failure in name resolution (SocketError)を解決したいです。

発生している問題・エラーメッセージ

]$ ruby scraping_title.rb
/home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/http.rb:879:in initialize': getaddrinfo: Temporary failure in name resolution (SocketE rror) from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/htt p.rb:879:inopen'
from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/htt p.rb:879:in block in connect' from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/timeout .rb:73:in timeout'
from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/htt p.rb:878:in connect' from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/htt p.rb:863:in do_start'
from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/2.2.0/net/htt p.rb:858:in start' from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/ge ms/net-http-persistent-2.9.4/lib/net/http/persistent.rb:700:in start'
from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/ge ms/net-http-persistent-2.9.4/lib/net/http/persistent.rb:631:in connect ion_for' from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/ge ms/net-http-persistent-2.9.4/lib/net/http/persistent.rb:994:in request '
from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/ge ms/mechanize-2.7.5/lib/mechanize/http/agent.rb:274:in fetch' from /home/vagrant/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/ge ms/mechanize-2.7.5/lib/mechanize.rb:464:in get'
from scraping_title.rb:4:in `<main>'

該当のソースコード

Ruby

require 'mechanize'

agent = Mechanize.new
page = agent.get("http://review-movie.herokuapp.com/")
elements = page.search('.entry-title a')
elements.each do |ele|
puts ele.inner_text
end