ConnectionAbortedError from Chrome cancelled preload

[William Hingston]

Using the following code in a ​service worker to preload:

addEventListener('activate', event => {
  event.waitUntil(async function() {
    // Feature-detect
    if (self.registration.navigationPreload) {
      // Enable navigation preloads!
      await self.registration.navigationPreload.enable();
    }
  }());
});

Gives the following error when the page is cached by the service worker and you F5 it attempts to preload and then cancels when the service worker boots up:

"C:\Program Files\JetBrains\PyCharm 2018.2.4\bin\runnerw.exe" C:\Users\Will\AppData\Local\Programs\Python\Python37-32\python.exe C:/Users/Will/PycharmProjects/lolnames.gg/manage.py runserver 8000
Performing system checks...

System check identified no issues (0 silenced).
October 21, 2018 - 12:21:51
Django version 2.1.2, using settings 'lolnamesgg.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
[21/Oct/2018 12:21:56] "GET /en/ HTTP/1.1" 200 11402
Traceback (most recent call last):
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 138, in run
    self.finish_response()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 180, in finish_response
    self.write(data)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 274, in write
    self.send_headers()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 332, in send_headers
    self.send_preamble()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 255, in send_preamble
    ('Date: %s\r\n' % format_date_time(time.time())).encode('iso-8859-1')
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 453, in _write
    result = self.stdout.write(data)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\socketserver.py", line 796, in write
    self._sock.sendall(b)
ConnectionAbortedError: [WinError 10053] An established connection was aborted by the software in your host machine
[21/Oct/2018 12:21:56] "GET /en/ HTTP/1.1" 500 59
----------------------------------------
Exception happened during processing of request from ('127.0.0.1', 51128)
Traceback (most recent call last):
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 138, in run
    self.finish_response()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 180, in finish_response
    self.write(data)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 274, in write
    self.send_headers()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 332, in send_headers
    self.send_preamble()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 255, in send_preamble
    ('Date: %s\r\n' % format_date_time(time.time())).encode('iso-8859-1')
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 453, in _write
    result = self.stdout.write(data)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\socketserver.py", line 796, in write
    self._sock.sendall(b)
ConnectionAbortedError: [WinError 10053] An established connection was aborted by the software in your host machine

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 141, in run
    self.handle_error()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\servers\basehttp.py", line 86, in handle_error
    super().handle_error()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 368, in handle_error
    self.finish_response()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 180, in finish_response
    self.write(data)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 274, in write
    self.send_headers()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 331, in send_headers
    if not self.origin_server or self.client_is_modern():
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 344, in client_is_modern
    return self.environ['SERVER_PROTOCOL'].upper() != 'HTTP/0.9'
TypeError: 'NoneType' object is not subscriptable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\socketserver.py", line 647, in process_request_thread
    self.finish_request(request, client_address)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\socketserver.py", line 357, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\socketserver.py", line 717, in __init__
    self.handle()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\servers\basehttp.py", line 154, in handle
    handler.run(self.server.get_app())
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\handlers.py", line 144, in run
    self.close()
  File "C:\Users\Will\AppData\Local\Programs\Python\Python37-32\lib\wsgiref\simple_server.py", line 35, in close
    self.status.split(' ',1)[0], self.bytes_sent
AttributeError: 'NoneType' object has no attribute 'split'
----------------------------------------

Windows 10
Chrome 70
Django 2.1
Python 3.7

[Tim Graham]

Do you have any idea about the root cause? Is Django definitely at fault or could it be a Python issue?

[Tim Graham]

If someone can demonstrate why Django is at fault and offer a patch, please reopen.