如何解决捆绑无法使用Capistrano 2.12找到rake 10.4.2

Question

嗨大家在将我的rails应用程序部署到amazon服务器时出现以下错误。我尝试了各种选择但失败了。错误是：

 ** transaction: commit
 * executing `deploy:restart'
 * executing "service unicorn-app-development restart"
   servers: ["localhost"]
   [localhost] executing command
 ** [out :: localhost] Couldn't reload, starting 'cd      /home/ubuntu/applications/app/development/current/app; bin/unicorn -D -c /home/ubuntu/applications/app/development/current/app/config/unicorn.rb -E development' instead
 ** [out :: localhost] 
 ** [out :: localhost] Could not find rake-10.4.2 in any of the sources
 ** [out :: localhost] 
 ** [out :: localhost] Run `bundle install` to install missing gems.
 ** [out :: localhost] 
    command finished in 247ms
 failed: "env RUBY_VERSION=ruby-2.1.2 GEM_HOME=/home/ubuntu/.rvm/gems/ruby-2.1.2@app GEM_PATH=/home/ubuntu/.rvm/gems/ruby-2.1.2@app:/home/ubuntu/.rvm/gems/ruby-2.1.2@global PATH=/home/ubuntu/.rvm/gems/ruby-2.1.2@app/bin:/home/ubuntu/.rvm/gems/ruby-2.1.2@global/bin:/home/ubuntu/.rvm/rubies/ruby-2.1.2/bin:/home/ubuntu/.rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games sh -c 'service unicorn-app-development restart'" on localhost

我的Gemfile包含：

 ##
 # Server and deployment
 gem 'unicorn'
 gem 'capistrano', '2.12'
 gem 'capistrano-ext'

我的deploy.rb看起来像

# config valid only for current version of Capistrano
require 'capistrano/ext/multistage'
require "bundler/capistrano"
set :application, 'app'
set :repository, 'git@bitbucket.org:username/app.git'
set :user, "ubuntu"
set :ssh_options, { :forward_agent => true }
set :stages, %w(development staging production)
set :default_stage, "development"

default_run_options[:pty] = true
set :use_sudo, false
set :deploy_via, :remote_cache
set :keep_releases, 5
set :scm, :git
set :scm_verbose, true

set :default_environment, {
                        'RUBY_VERSION' => ENV['RUBY_VERSION'],
                        'GEM_HOME' => ENV['GEM_HOME'],
                        'GEM_PATH' => ENV['GEM_PATH'],
                        'PATH' => ENV['PATH'],
                        'BUNDLE_PATH' => ENV['GEM_PATH'],
                    }

require 'bundler/capistrano'

namespace :nginx do
  %w[start stop restart].each do |command|
    desc "#{command} nginx server"
    task command, roles: :app, except: { no_release: true } do
      sudo "service nginx #{command}"
    end
  end
end

namespace :deploy do
  task :cold do
    update
    start
  end

  desc "restart unicorn"
  task :restart, roles: :app, except: { no_release: true } do
    run "service unicorn-#{application}-development restart"
  end

  %w[start stop].each do |command|
    desc "#{command} unicorn"
    task command, roles: :app, except: { no_release: true } do
      run "/etc/init.d/unicorn-#{application}-development #{command}"
    end
  end

  desc "Bundle deployment"
  task :bundle_deployment, roles: :app do
    run "cd #{release_path}/app && RAILS_ENV=development  bundle install"
  end

end

捆绑部署任务也无效。我正在使用rails-4.2.0版本。如何解决此错误。