Hi,

  I tried testing the CentOS upgrade rpms and documentation, by trying to upgrade a (freshly installed) CentOS 6 virtual box image to CentOS 7.

I tried following the steps described at http://wiki.centos.org/TipsAndTricks/CentOSUpgradeTool as closely as possible. 

  There was just one minor hiccup. I had to disable gpgcheck after running, centos-upgrade-tool-cli because of the attached error.