def essence_errors
      essence_errors = {}
      contents.each do |content|
        if content.essence_validation_failed?
          essence_errors[content.name] = content.essence.validation_errors
        end
      end
      essence_errors
    end
def essence_errors
      essence_errors = {}
      contents.each do |content|
        if content.essence_validation_failed?
          essence_errors[content.name] = content.essence.validation_errors
        end
      end
      essence_errors
    end
Returns all essence errors in the format of:

   {
     content.name => [
       error_message_for_validation_1,
       error_message_for_validation_2
     ]
   }

 Get translated error messages with +Element#essence_error_messages+