This snippet of Puppet code configures an Ubuntu system to use the Havana packages from the Ubuntu Cloud Archive as an apt repository.

apt-source-uca-havana

apt::source { 'ubuntu-cloud':
  location          =>  'http://ubuntu-cloud.archive.canonical.com/ubuntu',
  repos             =>  'main',
  release           =>  'precise-updates/havana',
  include_src       =>  false,
  required_packages =>  'ubuntu-cloud-keyring',
}