title: Cannot define multiple 'included' blocks for a Concern (ActiveSupport::Concern::MultipleIncludedBlocks) with cache_classes = true
body: <p>I have a certain module which is used in a Rails 4.1.1 application </p>
  
  <pre><code>module A
     extend ActiveSupport::Concern
     included do
       #Some code
     end
  end
  </code></pre>
  
  <p>which is included in a class</p>
  
  <pre><code>class Some
    include A
  end
  </code></pre>
  
  <p>This works great with <code>cache_classes=true</code> in <code>application.rb</code>. Now, if I turn off the caching of classes, I get <code>Cannot define multiple 'included' blocks for a Concern (ActiveSupport::Concern::MultipleIncludedBlocks)</code> exception upson starting the server.</p>
  
  <p>How should one deal with such an issue since reloading the classes is done by Rails?</p>