Rake generate_session_store error with Gemfile

I am trying to make a website live through hostgator and I am following their instructions

When I go to step 5.6 where I enter rake generate_session_store in SSH I get the error

There was an error in your Gemfile and Bundler cannot proceed.

I cannot figure out what I am doing wrong. If anyone can help me, we would be very grateful.

My current gemfile:

source 'https://rubygems.org'

gem "rake", "0.8.7"
gem "rack", "1.1.0"
gem "i18n", "0.4.2"
gem "rubytree", "0.5.2", :require => "tree"
gem "RedCloth", "~>4.2.3", :require => "redcloth" # for CodeRay
gem "mysql"
gem "coderay", "~>0.9.7"
gem "rdoc", "~>2.4.2"

gem 'rails',        '4.2.0'
gem 'bcrypt',       '3.1.7'
gem 'bootstrap-sass', '3.2.0.0'
gem 'sass-rails',   '5.0.2'
gem 'uglifier',     '2.5.3'
gem 'coffee-rails', '4.1.0'
gem 'jquery-rails', '4.0.3'
gem 'turbolinks',   '2.3.0'
gem 'jbuilder',     '2.2.3'
gem 'sdoc',         '0.4.0', group: :doc

#gem 'acts_as_shopping_cart', '~> 0.2.1'
 gem 'selenium-webdriver', '~> 2.46.2'
 gem 'activerecord', '~> 4.2.0'
 gemspec


 gem 'activemerchant'



 group :development, :test do
  gem 'sqlite3',     '1.3.9'
  gem 'byebug',      '3.4.0'
  gem 'web-console', '2.0.0.beta3'
  gem 'spring',      '1.1.3'
end

group :test do
  gem 'minitest-reporters', '1.0.5'
  gem 'mini_backtrace',     '0.1.3'
  gem 'guard-minitest',     '2.3.1'
  gem 'cucumber-rails', :require => false
  # database_cleaner is not required, but highly recommended
  #gem 'database_cleaner'
end

group :production do
  gem 'pg',             '0.17.1'
  gem 'rails_12factor', '0.0.2'
  gem 'puma',           '2.11.1'
end