I got error SSHKit::Runner::ExecuteError: Exception while executing on host XXX.XXX.XX.XX: exit>

Rails application when iam type cap production deploy it got a erro

production.rb

set :stage, :production
set :branch, "master"

# This is used in the Nginx VirtualHost to specify which domains
# the app should appear on. If you don't yet have DNS setup, you'll
# need to create entries in your local Hosts file for testing.
set :server_name, "XXX.XXX.XX.XX"

# used in case we're deploying multiple versions of the same
# app side by side. Also provides quick sanity checks when looking
# at filepaths
set :full_app_name, "#{fetch(:application)}_#{fetch(:stage)}"

server 'XXX.XXX.XX.XX', user: 'deploy', roles: %w{web app db}, primary: true

set :deploy_to, "/home/#{fetch(:deploy_user)}/apps/#{fetch(:full_app_name)}"

# dont try and infer something as important as environment from
# stage name.
set :rails_env, :production

# number of unicorn workers, this will be reflected in
# the unicorn.rb and the monit configs
set :unicorn_worker_count, 5

# whether we're using ssl or not, used for building nginx
# config file
set :enable_ssl, false

deploy.rb

set :application, 'appdy'
set :deploy_user, 'deploy'

# setup repo details
#set :scm, :git
#set :repo_url, 'git@github.com:username/repo.git'

# setup rbenv.
set :rbenv_type, :system
set :rbenv_ruby, '2.1.2'
set :rbenv_prefix, "RBENV_ROOT=#{fetch(:rbenv_path)} RBENV_VERSION=#{fetch(:rbenv_ruby)} #{fetch(:rbenv_path)}/bin/rbenv exec"
set :rbenv_map_bins, %w{rake gem bundle ruby rails}

# how many old releases do we want to keep, not much
set :keep_releases, 5

# files we want symlinking to specific entries in shared
set :linked_files, %w{config/database.yml}

# dirs we want symlinking to shared
set :linked_dirs, %w{bin log tmp/pids tmp/cache tmp/sockets vendor/bundle public/system}

# what specs should be run before deployment is allowed to
# continue, see lib/capistrano/tasks/run_tests.cap
#set :tests, []

# which config files should be copied by deploy:setup_config
# see documentation in lib/capistrano/tasks/setup_config.cap
# for details of operations
set(:config_files, %w(
  nginx.conf
  database.example.yml
  log_rotation
  unicorn.rb
  unicorn_init.sh
))

# which config files should be made executable after copying
# by deploy:setup_config
set(:executable_config_files, %w(
  unicorn_init.sh
))


# files which need to be symlinked to other parts of the
# filesystem. For example nginx virtualhosts, log rotation
# init scripts etc. The full_app_name variable isn't
# available at this point so we use a custom template {{}}
# tag and then add it at run time.
set(:symlinks, [
  {
    source: "nginx.conf",
    link: "/etc/nginx/sites-enabled/{{full_app_name}}"
  },
  {
    source: "unicorn_init.sh",
    link: "/etc/init.d/unicorn_{{full_app_name}}"
  },
  {
    source: "log_rotation",
   link: "/etc/logrotate.d/{{full_app_name}}"
  }
])

# this:
# http://www.capistranorb.com/documentation/getting-started/flow/
# is worth reading for a quick overview of what tasks are called
# and when for `cap stage deploy`

namespace :deploy do
  # make sure we're deploying what we think we're deploying
  before :deploy, "deploy:check_revision"
  # only allow a deploy with passing tests to deployed
  #before :deploy, "deploy:run_tests"
  # compile assets locally then rsync
  #after 'deploy:symlink:shared', 'deploy:compile_assets_locally'
  after :finishing, 'deploy:cleanup'

  # remove the default nginx configuration as it will tend
  # to conflict with our configs.
  before 'deploy:setup_config', 'nginx:remove_default_vhost'

  # reload nginx to it will pick up any modified vhosts from
  # setup_config
  after 'deploy:setup_config', 'nginx:reload'

  # Restart monit so it will pick up any monit configurations
  # we've added
  #after 'deploy:setup_config', 'monit:restart'

  # As of Capistrano 3.1, the `deploy:restart` task is not called
  # automatically.
  after 'deploy:publishing', 'deploy:restart'
end

gem File

# Use unicorn as the app server
gem 'unicorn'

# Use Capistrano for deployment
group :development do
	gem 'capistrano-rails'
	gem 'capistrano-bundler'
	gem 'capistrano-rbenv', "~> 2.0"
end

I am using sunzi gem and easy setup for Capistrano https://github.com/TalkingQuickly/capistrano-3-rails-template