class ActionDispatch::ShowExceptions

def render_exception(request, exception)
  backtrace_cleaner = request.get_header "action_dispatch.backtrace_cleaner"
  wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
  status  = wrapper.status_code
  request.set_header "action_dispatch.exception", wrapper.unwrapped_exception
  request.set_header "action_dispatch.original_path", request.path_info
  request.set_header "action_dispatch.original_request_method", request.raw_request_method
  fallback_to_html_format_if_invalid_mime_type(request)
  request.path_info = "/#{status}"
  request.request_method = "GET"
  response = @exceptions_app.call(request.env)
  response[1]["X-Cascade"] == "pass" ? pass_response(status) : response
rescue Exception => failsafe_error
  $stderr.puts "Error during failsafe response: #{failsafe_error}\n  #{failsafe_error.backtrace * "\n  "}"
  [500, { "Content-Type" => "text/plain" },
    ["500 Internal Server Error\n" \
    "If you are the administrator of this website, then please read this web " \
    "application's log file and/or the web server's log file to find out what " \
    "went wrong."]]
end