Do these steps on the node where you have installed Foreman:

1. yum install rubygem-nokogiri

2. gem install deface -v 0.7.2 --ignore-dependencies

3. git clone git://github.com/theforeman/foreman_simplify.git /usr/local/foreman_simplify

4. Put this into /usr/share/foreman/bundler.d/foreman_simplify.rb:

   gem 'deface', '0.7.2'
   gem 'foreman_simplify', :path => '/usr/local/foreman_simplify'
   

5. Run bundle as user foreman in the /usr/share/foreman directory.