Capistrano 3 deploy confirmation

gistfile1.rb

namespace :deploy do
  task :confirmation do
    puts <<-WARN

    ========================================================================

      WARNING: You're about to perform actions on production server(s)
      Please confirm that all your intentions are kind and friendly

    ========================================================================

    WARN
    ask :value, "Are you sure you want to continue? (Y)"

    if fetch(:value) != 'Y'
      puts "\nDeploy cancelled!"
      exit
    end
  end
end

Capistrano::DSL.stages.each do |stage|
  after stage, 'deploy:confirmation' if stage == 'production'
end