This terrible thing does not work

dev_gemfile.rb

DEV_GEMS = lambda do
  group :development, :test do
    gem 'ruby-debug-base19', '0.11.24'
    gem 'ruby-debug19', '0.11.6'
    gem 'factory_girl_rails'
    gem 'rails3-generators'
    gem 'thin'
    gem 'pickler', '~> 0.1.7'
  end

  group :test do
    gem 'capybara', '~> 0.3.9'
    gem 'cucumber-rails', '0.3.2'
    gem 'launchy'
    gem 'rspec', '2.0.0.beta.20'
    gem 'rspec-core', '2.0.0.beta.20'
    gem 'rspec-mocks', '2.0.0.beta.20'
    gem 'rspec-expectations', '2.0.0.beta.20'
    gem 'rspec-rails', '2.0.0.beta.20'
    gem 'shoulda', '2.11.3'
  end
end

Gemfile

require File.join(File.dirname(__FILE__),'dev_gemfile') 

source 'http://rubygems.org'

gem 'bundler', '~> 1.0.0'
gem 'decent_exposure', '~> 1.0.0.rc1'
gem 'devise', '~> 1.1.2'
gem 'haml'
gem 'hassle', :git => 'git://github.com/Papipo/hassle.git'
gem 'pg'
gem 'rails', '3.0.0'

DEV_GEMS.call unless ENV.any?{|key| key =~ /^HEROKU_/}

gistfile3.txt