Where has ActionController::Dispatcher gone in a Rails 3.1 console?

gistfile1.txt

Loading development environment (Rails 3.0.9)

ruby-1.9.2-p290 :001 > env = Rack::MockRequest.env_for('/')
 => {"rack.version"=>[1, 1], "rack.input"=>#<StringIO:0x00000102bfa628>, "rack.errors"=>#<StringIO:0x00000102bfa6c8>, "rack.multithread"=>true, "rack.multiprocess"=>true, "rack.run_once"=>false, "REQUEST_METHOD"=>"GET", "SERVER_NAME"=>"example.org", "SERVER_PORT"=>"80", "QUERY_STRING"=>"", "PATH_INFO"=>"/", "rack.url_scheme"=>"http", "HTTPS"=>"off", "SCRIPT_NAME"=>"", "CONTENT_LENGTH"=>"0"}

ruby-1.9.2-p290 :002 > ActionController::Dispatcher.new.call(env)
 => [200, {"Last-Modified"=>"Wed, 03 Aug 2011 13:08:10 GMT", "Content-Type"=>"text/html", "Content-Length"=>"5780"}, #<Rack::File:0x00000102f7a230 @root="/Users/testuser/Documents/Personal/Source/dispatch-test-rails3-stable/public", @path_info="/index.html", @path="/Users/testuser/Documents/Personal/Source/dispatch-test-rails3-stable/public/index.html">]



Loading development environment (Rails 3.1.0.rc5)

ruby-1.9.2-p290 :001 > env = Rack::MockRequest.env_for('/')
 => {"rack.version"=>[1, 1], "rack.input"=>#<StringIO:0x00000102caa230>, "rack.errors"=>#<StringIO:0x00000102caa2f8>, "rack.multithread"=>true, "rack.multiprocess"=>true, "rack.run_once"=>false, "REQUEST_METHOD"=>"GET", "SERVER_NAME"=>"example.org", "SERVER_PORT"=>"80", "QUERY_STRING"=>"", "PATH_INFO"=>"/", "rack.url_scheme"=>"http", "HTTPS"=>"off", "SCRIPT_NAME"=>"", "CONTENT_LENGTH"=>"0"} 

ruby-1.9.2-p290 :002 > ActionController::Dispatcher.new.call(env)
NameError: uninitialized constant ActionController::Dispatcher
        from (irb):2
        from /Users/testuser/.rvm/gems/ruby-1.9.2-p290@rails31/gems/railties-3.1.0.rc5/lib/rails/commands/console.rb:45:in `start'
        from /Users/testuser/.rvm/gems/ruby-1.9.2-p290@rails31/gems/railties-3.1.0.rc5/lib/rails/commands/console.rb:8:in `start'
        from /Users/testuser/.rvm/gems/ruby-1.9.2-p290@rails31/gems/railties-3.1.0.rc5/lib/rails/commands.rb:40:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'

Calling a controller action:

env = Rack::MockRequest.env_for('/')
MyController.action(:index).call(env)
r.map { |e| puts e.class }
response = r[2]
response.body