module ActionController::Rescue

def process_action(*args) 

def process_action(*args)
  super
rescue Exception => exception
  request.env['action_dispatch.show_detailed_exceptions'] ||= show_detailed_exceptions?
  rescue_with_handler(exception) || raise(exception)
end

def rescue_with_handler(exception) 

def rescue_with_handler(exception)
  if (exception.respond_to?(:original_exception) &&
      (orig_exception = exception.original_exception) &&
      handler_for_rescue(orig_exception))
    exception = orig_exception
  end
  super(exception)
end

def show_detailed_exceptions?

requests in production still shows the detailed exception pages.
false, but someone may set it to `request.local?` so local
consider_all_requests_local is false. By default, it returns
exceptions must be shown. This method is only called when
Override this method if you want to customize when detailed 
def show_detailed_exceptions?
  false
end