Gem install from Vagrantfile

Vagrantfile.rb

require "rubygems"

# Install the Chef gem into the private Vagrant gem repo
CHEF_VERSION = '11.8.2'

def with_vagrant_gem_path
  @old_gem_path = ENV["GEM_PATH"]
  @old_gem_home = ENV["GEM_HOME"]
  Gem.paths = ENV["GEM_PATH"] = ENV["GEM_HOME"] = "#{ENV['HOME']}/.vagrant.d/gems"
  return yield
ensure
  ENV["GEM_PATH"] = @old_gem_path
  ENV["GEM_HOME"] = @old_gem_home
  Gem.paths = ENV
end

begin
  Gem::Specification.find_by_name('chef', CHEF_VERSION)
rescue Gem::LoadError
  require "rubygems/dependency_installer"
  with_vagrant_gem_path do
    installer = Gem::DependencyInstaller.new(:document => [], :prerelease => false)
    installer.install('chef', CHEF_VERSION)
  end
end

# This pulls in the knife.rb config
require 'chef'
Chef::Config.from_file(File.join(ENV['HOME'], '.chef', 'knife.rb'))

Vagrant.configure("2") do |config|
  config.vm.provision :chef_client do |chef|
    chef.chef_server_url = Chef::Config[:chef_server_url]
    chef.log_level = Chef::Config[:log_level]
    chef.validation_key_path = Chef::Config[:validation_key]
    chef.validation_client_name = Chef::Config[:validation_client_name]
  end
end