This bug was mentioned firstly here: https://bugzilla.redhat.com/show_bug.cgi?id=796528#c22 but since it's not related to the #796528 I'm putting it into separate BZ.

Steps to Reproduce:
1. stop aeolus-configserver service (but keep httpd running so proxy error is returned)
2. try to launch a deployable which uses configserver
3. you should get message "503 Service unavailable" - this message is not very descriptive
  
Expected results:
'Cannot connect to the config server' might be returned - this is returned if connection fails (apache is not running)

Additional info:
fix should be easy - we could extend app/models/instance.rb:add_instance_config! to catch 503 http code too, now it catches only connection errors:

    rescue Errno::ECONNREFUSED                                                  
      raise I18n.t 'deployments.errors.config_server_connection'                
    end