Comment 2 for bug 1297664

Workaround of Ubuntu 12.04:

   sudo apt-get --purge remove ruby-rvm
   sudo rm -rf /usr/share/ruby-rvm /etc/rvmrc /etc/profile.d/rvm.sh
   \curl -sSL https://get.rvm.io | bash -s stable
   source ~/.bash_profile # Or just open new session
   rvm install 1.9.3
   rvm use 1.9.3

And now before start building iso just use `rvm use 1.9.3` or set this Ruby as default:
  rvm --default use 1.9.3