Add 'json' to the Gemfile for Centos 7

Gemfile

@@ -7,6 +7,9 @@ gem 'omnibus', '~> 4.0'
 # software definitions, but you can clone/fork Chef's to get you started.
 gem 'omnibus-software', github: 'opscode/omnibus-software'
+# On Centos 7, we need to explicitly add 'json' to the Gemfile. ??
+gem 'json'
+
 # This development group is installed by default when you run `bundle install`,
 # but if you are using Omnibus in a CI-based infrastructure, you do not need
 # the Test Kitchen-based build lab. You can skip these unnecessary dependencies

Gemfile.lock

@@ -141,6 +141,7 @@ PLATFORMS
 DEPENDENCIES
   berkshelf (~> 3.0)
+  json
   kitchen-vagrant (~> 0.14)
   omnibus (~> 4.0)
   omnibus-software!