Simple Tornado server sending 500 reponses

server.py

import tornado.httpserver
import tornado.ioloop
import tornado.web


class Handler(tornado.web.RequestHandler):
  def error(self):
    self.set_header("Access-Control-Allow-Credentials", "true")
    self.set_header("Access-Control-Allow-Origin", "")
    self.set_header("Access-Control-Allow-Methods", "GET, POST")
    self.set_status(500)
    self.write('Server Error')

  def get(self):
    self.error()
  def post(self):
    self.error()


app = tornado.web.Application([
  (r".+", Handler),
])

if __name__ == "__main__":
  # uncomment for HTTPS
  # server = tornado.httpserver.HTTPServer(app, ssl_options={
  #   "certfile": "my.cert",
  #   "keyfile": "my.key"
  # })
  # server.listen(443)

  app.listen(80)
  tornado.ioloop.IOLoop.instance().start()