Support Python 3.12

[wxtim]

• Add tests to ensure that we test with the latest Python version.
• Make cylc report timings emit a warning that it is deprecated if Python < 3.12, else it is obsolete, and emit an error to that effect.
• Fix Flake 8 Failures.
• Replace smtpd (deprecated at Python 3.6, removed at 3.12) with aiosmtpd.

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included: PR is a test enhancement.
• CHANGES.md entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[MetRonnie]

P.S. the config change Involves a change to global or workflow config label is meant for changes that actually change the config

[MetRonnie]

One test failure

tests/unit/test_indep_task_queues.py::test_queue_and_release[active0-expected_released0-expected_foo_groups0] - AttributeError: 'called_with' is not a valid assertion. Use a spec for the mock if 'called_with' is meant to be an attribute.

[MetRonnie]

AttributeError: 'called_with' is not a valid assertion

diff --git a/tests/unit/test_indep_task_queues.py b/tests/unit/test_indep_task_queues.py
index a0a1894ce..7838a109e 100644
--- a/tests/unit/test_indep_task_queues.py
+++ b/tests/unit/test_indep_task_queues.py
@@ -94,6 +94,6 @@ def test_queue_and_release(
     # check released tasks change state to "preparing", and not is_queued
     for r in released:
-        assert r.state.reset.called_with(TASK_STATUS_PREPARING)
-        assert r.state.reset.called_with(is_queued=False)
+        r.state.reset.assert_called_with(TASK_STATUS_PREPARING)
+        r.state.reset.assert_called_with(is_queued=False)
 
     # check that adopted orphans end up in the default queue

[MetRonnie]

From Tim on Element:

Bother: I've found another problem with the Python 3.12 upgrade branch:

(tl;dr smtpd has been removed at Python 3.12: We need to use aiosmtpd - I'm investigating)

At 3.11

/home/tim/mambaforge/envs/cylc.dev.3.11/lib/python3.11/smtpd.py:96: DeprecationWarning: The asyncore module is deprecated and will be removed in Python 3.12. The recommended replacement is asyncio
  import asyncore
/home/tim/mambaforge/envs/cylc.dev.3.11/lib/python3.11/smtpd.py:97: DeprecationWarning: The asynchat module is deprecated and will be removed in Python 3.12. The recommended replacement is asyncio
  import asynchat
DebuggingServer started at Mon Nov  6 12:05:29 2023
	Local addr: ('localhost', 8025)
	Remote addr:('localhost', 25)

At 3.12

/home/tim/mambaforge/envs/cylc.dev/bin/python3: No module named smtpd

[oliver-sanders]

Ach dammit, I hadn't spotted the failing tests.

@wxtim, could you take a look at:

• tests/f/events/13-task-event-mail-globalcfg.t
• tests/f/events/29-task-event-mail-1.t
• tests/f/events/30-task-event-mail-2.t
• tests/f/events/09-task-event-mail.t

(now on master, mb)