Gemfile

source 'http://rubygems.org'
gem 'rails', '3.0.3'

group :development do
  gem 'rack-contrib', :require => 'rack/contrib'
end

shell transcript

# create empty gemset
$ rvm use @bundler_108 --create

# install bundler and rails
$ gem install bundler -v 1.0.8
$ gem install rails

# create new rails project
$ rails new my_test

# change into my_test and edit Gemfile to match above version
$ cd my_test
$ vi Gemfile

# Install gems and test app
$ bundle install
$ rake -T
(in /private/tmp/my_test)
rake aborted!
no such file to load -- rack/contrib
/private/tmp/my_test/Rakefile:4
(See full trace by running task with --trace)