task_finished signal logs "NoneType: None" when no exception is raised

[Jacob Walls]

The test provided on ​PR #20722 demonstrates that faux exceptions are logged as NoneType: None by the log_task_finished signal handler:

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FAIL: test_successful_task_no_none_type_in_logs (tasks.test_immediate_backend.ImmediateBackendTestCase.test_successful_task_no_none_type_in_logs)
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Traceback (most recent call last):
  File "/Users/jwalls/django/tests/tasks/test_immediate_backend.py", line 238, in test_successful_task_no_none_type_in_logs
    self.assertNotIn("NoneType", log_output)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'NoneType' unexpectedly found in 'INFO:django.tasks:Task id=1yKnLbcmTGMEUfj0B1JG0766LDM1Sono path=tasks.tasks.noop_task state=SUCCESSFUL\nNoneType: None'

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[Jacob Walls]

​PR

[Jacob Walls]

Opening the ticket as a courtesy, accepting as a triager.

[Jacob Walls <jacobtylerwalls@…>]

In 497d9cdc:

Fixed #36951 -- Removed empty exc_info from log_task_finished signal handler.

Before, if no exception occurred, "None Type: None" was logged.

[Jacob Walls <jacobtylerwalls@…>]

In 3a04b22:

[6.0.x] Fixed #36951 -- Removed empty exc_info from log_task_finished signal handler.

Before, if no exception occurred, "None Type: None" was logged.

Backport of 497d9cdc67f0bdae929fcde677b5f441e94a6c8b from main.