Port TestFileTaskLogHandler tests to new Structlog logs

[highlyavailable]

Fixes #50977

Problem

Two TestFileTaskLogHandler tests were marked with @pytest.mark.xfail because they were written for the old logging format but needed to work with the new structlog-based logging system:

• test_file_task_handler_when_ti_value_is_invalid
• test_file_task_handler

These tests were failing because they expected log data as strings but were receiving StructuredLogMessage objects from the new structlog implementation.

Solution

1. Removed @pytest.mark.xfail decorators - (tests now pass instead of being marked as expected failures)

2. Updated test_file_task_handler assertion logic:

   • Before: assert re.search(target_re, log_content) (regex matching on string content)
   • After: assert any("test" in event for event in events(logs)) (substring matching on event messages)

3. No changes needed for test_file_task_handler_when_ti_value_is_invalid - This test actually already used direct object access (logs[0].event) which works correctly with StructuredLogMessage objects

[boring-cyborg]

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[kaxil]

Tests are failing:

FAILED airflow-core/tests/unit/utils/test_log_handlers.py::TestFileTaskLogHandler::test_file_task_handler_when_ti_value_is_invalid - AttributeError: 'RuntimeTaskInstance' object has no attribute 'log'
FAILED airflow-core/tests/unit/utils/test_log_handlers.py::TestFileTaskLogHandler::test_file_task_handler - AttributeError: 'RuntimeTaskInstance' object has no attribute 'log'

[highlyavailable]

Tests are failing:

FAILED airflow-core/tests/unit/utils/test_log_handlers.py::TestFileTaskLogHandler::test_file_task_handler_when_ti_value_is_invalid - AttributeError: 'RuntimeTaskInstance' object has no attribute 'log'
FAILED airflow-core/tests/unit/utils/test_log_handlers.py::TestFileTaskLogHandler::test_file_task_handler - AttributeError: 'RuntimeTaskInstance' object has no attribute 'log'

Hey @kaxil, this commit fixes the failing tests. Thanks for the feedback.

[kaxil]

Thanks, I have rebased your PR on main, let's see what the CI says

[o-nikolas]

Nice fix, thanks for circling back and ensuring these tests pass :)

[uranusjr]

Should this use structlog.get_logger instead?

[github-actions]

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