Rails 3.1.2 - Bundler could not find compatible versions for gem "railties"

Question

I am trying to install the new version of the twitter-bootstrap-rails gem (v2), but getting the error above. This is how my Gemfile looks:

source 'http://rubygems.org'

gem 'rails', '3.1.2'

# Bundle edge Rails instead:
# gem 'rails',     :git => 'git://github.com/rails/rails.git'


gem 'mysql2'
gem 'authlogic'
gem "paperclip", "~> 2.4.5"
gem 'aws-s3'
gem 'actionmailer'
gem "twitter-bootstrap-rails", "~> 2.0"
gem 'sunspot_rails'

#endless page
gem 'will_paginate'

# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails',   '~> 3.1.5.rc.2'
  gem 'coffee-rails', '~> 3.1.1'
  gem 'uglifier', '>= 1.0.3'
end

group :production do
  gem 'therubyracer-heroku', '~> 0.8.1.pre3'
  gem 'pg'
  gem 'thin'
end

group :development do
  gem "taps", "~> 0.3.23"
  gem "rvm", "~> 1.9.2"
end

gem 'jquery-rails'

# To use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.0.0'

# Use unicorn as the web server
# gem 'unicorn'

# Deploy with Capistrano
# gem 'capistrano'

# To use debugger
# gem 'ruby-debug19', :require => 'ruby-debug'

And complete error:

Bundler could not find compatible versions for gem "railties":
  In Gemfile:
    twitter-bootstrap-rails (~> 2.0) ruby depends on
      railties (>= 3.2.1) ruby

    sass-rails (~> 3.1.5.rc.2) ruby depends on
      railties (3.1.0)

What is wrong? When I remove the version ~> 2.0 from the gem, it works, but I need the new version of bootstrap...

EDIT: bundle install

Bundler could not find compatible versions for gem "railties":
  In snapshot (Gemfile.lock):
    railties (3.1.2)

  In Gemfile:
    twitter-bootstrap-rails (~> 2.0) ruby depends on
      railties (>= 3.2.1) ruby

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

Answer 1

Solution:

gem 'rails', '3.2.1'
gem "sass-rails", "~> 3.2.4"
gem "coffee-rails", "~> 3.2.2"

And then

bundle update

Answer 2

The answer is in Bundler's output. Your project is using Rails 3.1.2, which requires railties 3.1.2. The version of twitter-bootstrap-rails you are trying to install apparently depends on railties >= 3.2.1, which you don't have.

You have three options, from the looks of it:

1. Take a look at the twitter-bootstrap-rails repo and take note of the fact that it looks like they are trying to lower the dependencies back to >= 3.1. Wait for a new version to be released or use their master branch.
2. Upgrade your project to use Rails 3.2
3. Use an older version of twitter-bootstrap-rails that still works with Rails 3.1.