title: rails 4 + mina deployment failure
body: <p>i am deploying a rails 4 application using mina deployment. my deployment script is as</p>
  
  <pre><code>require 'mina/bundler'
  require 'mina/rails'
  require 'mina/git'
  require 'mina/rvm'    # for rvm support. (http://rvm.io)
  
  set :domain, 'someplace.com'
  set :deploy_to, '/home/deploy/projects/website'
  set :repository, 'git@github.com:someone/repo.git'
  set :branch, 'master'
  
  set :identity_file, "#{ENV['HOME']}/.ssh/id_rsa"
  set :user, 'deploy'    # Username in the server to SSH to.
  
  set :shared_paths, ['config/database.yml', 'config/credentials.yml', 'log', 'tmp']
  
  task :environment do
    invoke :'rvm:use[ruby-2.1.0@default]'
  end
  
  task :setup =&gt; :environment do
    queue! %[mkdir -p "#{deploy_to}/shared/log"]
    queue! %[chmod g+rx,u+rwx "#{deploy_to}/shared/log"]
  
    queue! %[mkdir -p "#{deploy_to}/shared/config"]
    queue! %[chmod g+rx,u+rwx "#{deploy_to}/shared/config"]
  
    queue! %[touch "#{deploy_to}/shared/config/database.yml"]
    queue  %[echo "-----&gt; Be sure to edit 'shared/config/database.yml'."]
  
    queue! %[touch "#{deploy_to}/shared/config/credentials.yml"]
    queue  %[echo "-----&gt; Be sure to edit 'shared/config/credentials.yml'."]
  end
  
  desc "Deploys the current version to the server."
  task :deploy =&gt; :environment do
    deploy do
      invoke :'git:clone'
      invoke :'deploy:link_shared_paths'
      invoke :'bundle:install'
      invoke :'rails:assets_precompile'
  
      to :launch do
        queue "touch #{deploy_to}/tmp/restart.txt"
      end
    end
  end
  </code></pre>
  
  <p>when i deploy as 'mina deploy', i get error as</p>
  
  <pre><code>...
  
  Symlinking shared paths
  $ mkdir -p "./config"
  $ mkdir -p "."
  $ rm -rf "./config/database.yml"
  $ ln -s "/home/deploy/projects/website/shared/config/database.yml" "./config/database.yml"
  $ rm -rf "./config/credentials.yml"
  $ ln -s "/home/deploy/projects/website/shared/config/credentials.yml" "./config/credentials.yml"
  $ rm -rf "./log"
  $ ln -s "/home/deploy/projects/website/shared/log" "./log"
  $ rm -rf "./tmp"
  $ ln -s "/home/deploy/projects/website/shared/tmp" "./tmp"
  
  -----&gt; Installing gem dependencies using Bundler
  $ mkdir -p "/home/deploy/projects/website/shared/bundle"
  $ mkdir -p "./vendor"
  $ ln -s "/home/deploy/projects/website/shared/bundle" "./vendor/bundle"
  $ bundle install --without development:test --path "./vendor/bundle" --binstubs bin/ --deployment
  
  ...
  
  Your bundle is complete!
  Gems in the groups development and test were not installed.
  It was installed into ./vendor/bundle
  
  -----&gt; Precompiling asset files
  $ RAILS_ENV="production" bundle exec rake assets:precompile RAILS_GROUPS=assets
  rake aborted!
  File exists @ dir_s_mkdir - /home/deploy/projects/website/tmp/build-138935597031149/tmp
  /home/deploy/projects/website/tmp/build-138935597031149/vendor/bundle/ruby/2.1.0/gems/sprockets-2.10.1/lib/sprockets/cache/file_store.rb:25:in `[]='
  /home/deploy/projects/website/tmp/build-138935597031149/vendor/bundle/ruby/2.1.0/gems/sprockets-2.10.1/lib/sprockets/caching.rb:34:in `cache_set'
  </code></pre>