title: uninitialized constant while calling ImageWorker in sidekiq
body: <p>In my <code>Banner</code> model, I called this:</p>
  
  <pre><code>after_save :enqueue_image   
  
    def enqueue_image
      ImageWorker.perform_async(id, key) if key.present?
    end
  
  class ImageWorker
    include Sidekiq::Worker
  
    def perform(id, key)
      banner = Banner.find(id)
      banner.key = key
      banner.remote_image_url = banner.image.direct_fog_url(with_path: true)
      banner.save!
    end
  end
  </code></pre>
  
  <p>The error I am getting in <code>sidekiq</code> is this:</p>
  
  <pre><code>2012-11-16T12:30:35Z 75701 TID-ows7fyu3w WARN: {"retry"=&gt;true, "queue"=&gt;"default", "class"=&gt;"Banner::ImageWorker", "args"=&gt;[6, "uploads/af-64b9e8b8c96a/770x350.gif"], "jid"=&gt;"b8f23a2387f2b751"}
  2012-11-16T12:30:35Z 75701 TID-ows7fyu3w WARN: uninitialized constant Banner::ImageWorker
  2012-11-16T12:30:35Z 75701 TID-ows7fyu3w WARN: /.rvm/gems/ruby-1.9.3-p194@myapp/gems/activesupport-3.2.8/lib/active_support/inflector/methods.rb:230:in `block in constantize'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/activesupport-3.2.8/lib/active_support/inflector/methods.rb:229:in `each'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/activesupport-3.2.8/lib/active_support/inflector/methods.rb:229:in `constantize'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/activesupport-3.2.8/lib/active_support/core_ext/string/inflections.rb:54:in `constantize'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/sidekiq-2.5.3/lib/sidekiq/processor.rb:37:in `block in process'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/celluloid-0.12.3/lib/celluloid/calls.rb:57:in `call'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/celluloid-0.12.3/lib/celluloid/calls.rb:57:in `dispatch'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/celluloid-0.12.3/lib/celluloid/future.rb:18:in `block in initialize'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/celluloid-0.12.3/lib/celluloid/internal_pool.rb:48:in `call'
  /.rvm/gems/ruby-1.9.3-p194@myapp/gems/celluloid-0.12.3/lib/celluloid/internal_pool.rb:48:in `block in create'
  </code></pre>