Add support for Python 3.14

[willingc]

🚀 Feature

Support Python 3.14.

[willingc]

Test results on Python 3.14

_________________________________________ TestBrokenNotebook1.test __________________________________________

self = <papermill.tests.test_execute.TestBrokenNotebook1 testMethod=test>

    def test(self):
        path = get_notebook_path('broken1.ipynb')
    
        # check that the notebook has two existing marker cells, so that this test is sure to be
        # validating the removal logic (the markers are simulating an error in the first code cell
        # that has since been fixed)
        original_nb = load_notebook_node(path)
        self.assertEqual(original_nb.cells[0].metadata["tags"], ["papermill-error-cell-tag"])
        self.assertIn("In [1]", original_nb.cells[0].source)
        self.assertEqual(original_nb.cells[2].metadata["tags"], ["papermill-error-cell-tag"])
    
        result_path = os.path.join(self.test_dir, 'broken1.ipynb')
        with self.assertRaises(PapermillExecutionError):
            execute_notebook(path, result_path)
        nb = load_notebook_node(result_path)
        self.assertEqual(nb.cells[0].cell_type, "markdown")
        self.assertRegex(nb.cells[0].source, r'^<span .*<a href="#papermill-error-cell".*In \[2\].*</span>$')
        self.assertEqual(nb.cells[0].metadata["tags"], ["papermill-error-cell-tag"])
    
        self.assertEqual(nb.cells[1].cell_type, "markdown")
        self.assertEqual(nb.cells[2].execution_count, 1)
        self.assertEqual(nb.cells[3].cell_type, "markdown")
        self.assertEqual(nb.cells[4].cell_type, "markdown")
    
        self.assertEqual(nb.cells[5].cell_type, "markdown")
        self.assertRegex(nb.cells[5].source, '<span id="papermill-error-cell" .*</span>')
        self.assertEqual(nb.cells[5].metadata["tags"], ["papermill-error-cell-tag"])
        self.assertEqual(nb.cells[6].execution_count, 2)
>       self.assertEqual(nb.cells[6].outputs[0].output_type, 'error')
E       AssertionError: 'stream' != 'error'
E       - stream
E       + error

papermill/tests/test_execute.py:162: AssertionError
------------------------------------------- Captured stderr call --------------------------------------------
Executing:  83%|██████████████████████████████████████████████████          | 5/6 [00:00<00:00,  6.60cell/s]
============================================= warnings summary ==============================================
papermill/tests/test_iorw.py::TestPapermillIO::test_read
papermill/tests/test_iorw.py::TestPapermillIO::test_write
  /Users/willingc/Code/repos-nteract/papermill/papermill/iorw.py:149: UserWarning: the file is not specified with any extension : path
    warnings.warn(f"the file is not specified with any extension : {os.path.basename(path)}")

papermill/tests/test_iorw.py::TestPapermillIO::test_read_stdin
papermill/tests/test_iorw.py::TestPapermillIO::test_write_stdout
  /Users/willingc/Code/repos-nteract/papermill/papermill/iorw.py:149: UserWarning: the file is not specified with any extension : -
    warnings.warn(f"the file is not specified with any extension : {os.path.basename(path)}")

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
============================================== tests coverage ===============================================
_____________________________ coverage: platform darwin, python 3.14.0-final-0 ______________________________

Name                        Stmts   Miss  Cover
-----------------------------------------------
papermill/__init__.py           4      0   100%
papermill/__main__.py           1      1     0%
papermill/abs.py               33      0   100%
papermill/adl.py               34      0   100%
papermill/cli.py              116      4    97%
papermill/clientwrap.py        55      5    91%
papermill/engines.py          191      8    96%
papermill/exceptions.py        36      6    83%
papermill/execute.py           83      0   100%
papermill/inspection.py        57      0   100%
papermill/iorw.py             344     67    81%
papermill/log.py                2      0   100%
papermill/models.py             2      0   100%
papermill/parameterize.py      49      1    98%
papermill/s3.py               197     43    78%
papermill/translators.py      368      8    98%
papermill/utils.py             63      3    95%
-----------------------------------------------
TOTAL                        1635    146    91%
========================================== short test summary info ==========================================
FAILED papermill/tests/test_execute.py::TestBrokenNotebook1::test - AssertionError: 'stream' != 'error'
================================ 1 failed, 546 passed, 4 warnings in 54.76s =================================
py314: exit 1 (56.51 seconds) /Users/willingc/Code/repos-nteract/papermill> pytest -v --maxfail=2 --cov=papermill -W always pid=19907
  py314: FAIL code 1 (83.98=setup[27.47]+cmd[56.51] seconds)
  evaluation failed :( (84.02 seconds)

[costajohnt]

I'd like to work on this. Based on the test output, the fix involves updating TestBrokenNotebook1 (and potentially TestBrokenNotebook2) to handle Python 3.14's changed output ordering for assertion errors, plus adding 3.14 to the CI matrix, tox config, and pyproject.toml classifiers.