Do not try to use thor gem.

railties/lib/generators.rb

@@ -11,7 +11,7 @@
 
 $:.unshift(File.dirname(__FILE__))
 
-require 'vendor/thor'
+require 'vendor/thor-0.11.2/lib/thor'
 require 'generators/base'
 require 'generators/named_base'
 

railties/lib/vendor/thor.rb

-begin
-  # Prefer gems to the bundled libs.
-  require 'rubygems'
-  gem 'thor', '>= 0.11.2'
-rescue Gem::LoadError
-  $:.unshift "#{File.dirname(__FILE__)}/thor-0.11.2/lib"
-end
-
-require 'thor'