from telegram.ext import Updater
updater = Updater(TOKEN, use_context=True)
updater.start_webhook()
updater.idle()

Exception in thread Bot:377489430:updater:
Traceback (most recent call last):
  File "C:\Program Files\Python38\lib\threading.py", line 932, in _bootstrap_inner
    self.run()
  File "C:\Program Files\Python38\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\telegram\ext\updater.py", line 216, in _thread_wrapper
    target(*args, **kwargs)
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\telegram\ext\updater.py", line 452, in _start_webhook
    self.httpd.serve_forever()
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\telegram\utils\webhookhandler.py", line 52, in serve_forever
    self.http_server.listen(self.port, address=self.listen)
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\tornado\tcpserver.py", line 152, in listen
    self.add_sockets(sockets)
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\tornado\tcpserver.py", line 165, in add_sockets
    self._handlers[sock.fileno()] = add_accept_handler(
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\tornado\netutil.py", line 279, in add_accept_handler
    io_loop.add_handler(sock, accept_handler, IOLoop.READ)
  File "C:\Users\User\.virtualenvs\sandbox38\lib\site-packages\tornado\platform\asyncio.py", line 100, in add_handler
    self.asyncio_loop.add_reader(fd, self._handle_events, fd, IOLoop.READ)
  File "C:\Program Files\Python38\lib\asyncio\events.py", line 501, in add_reader
    raise NotImplementedError
NotImplementedError

certifi 2020.04.05.1
future 0.18.2
Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)]