Close proxy tunnel connection when TLS raises during CONNECT (#921)

[phanen]

Summary

Close proxy tunnel connection when TLS raises during CONNECT (#921)

This happened when I use python-telegram-bot library.

Details

The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File ".venv/lib/python3.13/site-packages/telegram/request/_httpxrequest.py", line 279, in do_request
    res = await self._client.request(
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<6 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/httpx/_client.py", line 1540, in request
    return await self.send(request, auth=auth, follow_redirects=follow_redirects)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpx/_client.py", line 1629, in send
    response = await self._send_handling_auth(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<4 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/httpx/_client.py", line 1657, in _send_handling_auth
    response = await self._send_handling_redirects(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/httpx/_client.py", line 1694, in _send_handling_redirects
    response = await self._send_single_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpx/_client.py", line 1730, in _send_single_request
    response = await transport.handle_async_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 393, in handle_async_request
    with map_httpcore_exceptions():
         ~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/root/.local/share/uv/python/cpython-3.13.12-linux-x86_64-gnu/lib/python3.13/contextlib.py", line 162, in __exit__
    self.gen.throw(value)
    ~~~~~~~~~~~~~~^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 118, in map_httpcore_exceptions
    raise mapped_exc(message) from exc
httpx.ConnectError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File ".venv/lib/python3.13/site-packages/telegram/ext/_utils/networkloop.py", line 161, in network_retry_loop
    await do_action()
  File ".venv/lib/python3.13/site-packages/telegram/ext/_utils/networkloop.py", line 154, in do_action
    action_cb_task.result()
    ~~~~~~~~~~~~~~~~~~~~~^^
  File ".venv/lib/python3.13/site-packages/telegram/ext/_updater.py", line 340, in polling_action_cb
    updates = await self.bot.get_updates(
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/ext/_extbot.py", line 672, in get_updates
    updates = await super().get_updates(
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<9 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/_bot.py", line 4865, in get_updates
    await self._post(
    ^^^^^^^^^^^^^^^^^
    ...<7 lines>...
    ),
    ^
  File ".venv/lib/python3.13/site-packages/telegram/_bot.py", line 704, in _post
    return await self._do_post(
           ^^^^^^^^^^^^^^^^^^^^
    ...<6 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/ext/_extbot.py", line 370, in _do_post
    return await super()._do_post(
           ^^^^^^^^^^^^^^^^^^^^^^^
    ...<6 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/_bot.py", line 733, in _do_post
    result = await request.post(
             ^^^^^^^^^^^^^^^^^^^
    ...<6 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/request/_baserequest.py", line 198, in post
    result = await self._request_wrapper(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<7 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/request/_baserequest.py", line 305, in _request_wrapper
    code, payload = await self.do_request(
                    ^^^^^^^^^^^^^^^^^^^^^^
    ...<7 lines>...
    )
    ^
  File ".venv/lib/python3.13/site-packages/telegram/request/_httpxrequest.py", line 303, in do_request
    raise NetworkError(f"httpx.{err.__class__.__name__}: {err}") from err
telegram.error.NetworkError: httpx.ConnectError:
Exception happened while polling for updates.
Traceback (most recent call last):
  File ".venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 101, in map_httpcore_exceptions
    yield
  File ".venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 394, in handle_async_request
    resp = await self._pool.handle_async_request(req)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 256, in handle_async_request
    raise exc from None
  File ".venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 236, in handle_async_request
    response = await connection.handle_async_request(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        pool_request.request
        ^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File ".venv/lib/python3.13/site-packages/httpcore/_async/http_proxy.py", line 316, in handle_async_request
    stream = await stream.start_tls(**kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpcore/_async/http11.py", line 376, in start_tls
    return await self._stream.start_tls(ssl_context, server_hostname, timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpcore/_backends/anyio.py", line 67, in start_tls
    with map_exceptions(exc_map):
         ~~~~~~~~~~~~~~^^^^^^^^^
  File "/root/.local/share/uv/python/cpython-3.13.12-linux-x86_64-gnu/lib/python3.13/contextlib.py", line 162, in __exit__
    self.gen.throw(value)
    ~~~~~~~~~~~~~~^^^^^^^
  File ".venv/lib/python3.13/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
    raise to_exc(exc) from exc

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• (N/A) I've updated the documentation accordingly.