title: why OmniAuth::Strategies::Facebook::NoAuthorizationCodeError is not handled in omniauth on_failure callback?
body: <p>I am using Omniauth for Rails 3.2.3 application.</p>
  
  <p>I have configured the on_failure callback as show below.</p>
  
  <pre><code>OmniAuth.config.on_failure = Proc.new do |env|
    UsersController.action(:omniauth_failure).call(env)
  end
  </code></pre>
  
  <p>This handles the error "OmniAuth::Strategies::CallbackError" but not "OmniAuth::Strategies::Facebook::NoAuthorizationCodeError".</p>
  
  <p>How to handle this error?.Surly I can not use rescue_from as the error happens in Rack level.</p>
  
  <p>Any ideas?</p>
  
  <p>Thank you</p>