Capistrano : Don't know how to build task 'deploy:restart'

Question

 bundle exec cap production deploy

At the end I get this error

ruby 2.0.0p353 (2013-11-22 revision 43784) [x86_64-linux]
cap aborted!
Don't know how to build task 'deploy:restart'

deploy.rb

namespace :deploy do

  desc 'Restart application'
  task :restart do
    on roles(:app), in: :sequence, wait: 5 do
      # Your restart mechanism here, for example:
       execute :touch, release_path.join('tmp/restart.txt')
    end
  end

  after :publishing, :restart

end

Capistrano 3.0

Answer 1

RESOLVED.

set :pty, true

set :keep_releases, 1

namespace :deploy do

  desc 'Restart application'
  task :restart do
    on roles(:app), in: :sequence, wait: 5 do
      # Your restart mechanism here, for example:
       execute :touch, release_path.join('tmp/restart.txt')
    end
  end

  after :restart, :clear_cache do
    on roles(:web), in: :groups, limit: 3, wait: 10 do
      # Here we can do anything such as:
      # within release_path do
      #   execute :rake, 'cache:clear'
      # end
    end
  end

  after :finishing, 'deploy:cleanup'


end