boot.rb

  class Boot
    def run
      load_initializer
      extend_environment
      Rails::Initializer.run(:set_load_path)
    end

    def extend_environment
      Rails::Initializer.class_eval do
        old_load = instance_method(:load_environment)
        define_method(:load_environment) do
          Bundler.require_env RAILS_ENV
          old_load.bind(self).call
        end
      end
    end
  end