Since Python 3.9, calling `smtplib.LMTP.connect()` without explicitly specifying any `timeout=` raises a `TypeError`. Specifying `None` or any integer value works correctly.

```
>>> import smtplib
>>> smtplib.LMTP("/tmp/lmtp.sock")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.9/smtplib.py", line 1071, in __init__
    super().__init__(host, port, local_hostname=local_hostname,
  File "/usr/lib/python3.9/smtplib.py", line 253, in __init__
    (code, msg) = self.connect(host, port)
  File "/usr/lib/python3.9/smtplib.py", line 1085, in connect
    self.sock.settimeout(self.timeout)
TypeError: an integer is required (got type object)
>>> l = smtplib.LMTP()
>>> l.connect("/tmp/lmtp.sock")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.9/smtplib.py", line 1085, in connect
    self.sock.settimeout(self.timeout)
TypeError: an integer is required (got type object)
```

Upon investigation with `pdb`, the default object for the `timeout` parameter (`socket._GLOBAL_DEFAULT_TIMEOUT`) is passed through to the `self.sock.settimeout` call, instead of being handled as "no timeout specified". The relevant changes were introduced as fix for bpo-39329.

Hello Wüstengecko,

Thanks for raising this issue. I've opened a PR which I believe will resolve the problem, but it's difficult to verify this against the mock socket setup. Feel free to leave feedback.

Hello,
I can confirm that the PR resolves the issue.
Thanks for the quick fix!

This

This is a regression bug that should be fixed.

New changeset 3bf05327c2b25d42b92795d9d280288c22a0963d by Ross in branch 'master':
bpo-42756: Configure LMTP Unix-domain socket to use global default timeout when timeout not provided (GH-23969)
https://github.com/python/cpython/commit/3bf05327c2b25d42b92795d9d280288c22a0963d

New changeset 69120613c071e9327a9dc6e4b1ff21b2e94d885e by Ross in branch '3.9':
[3.9] bpo-42756: Configure LMTP Unix-domain socket to use global default timeout when timeout not provided (GH-23969) (GH-24050)
https://github.com/python/cpython/commit/69120613c071e9327a9dc6e4b1ff21b2e94d885e

Thanks, Ross Rhodes for the fix!
And thanks, Wüstengecko for the report!