https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sec-Configuring_Yum_and_Yum_Repositories.html
https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/2/html/Getting_Started_Guide/sect-Configuring_Software_Repositories.html
http://docs.puppetlabs.com/references/latest/type.html#yumrepo