Updates round 2

[matthewhughes934]

Second round of updates, split out to keep PRs reasonable size

• Drop py dependency

  This package is in maintenance only mode and only had two uses. Replace
  their use with the tmp_path fixture as suggested in the docs[1]

  Link: https://docs.pytest.org/en/8.3.x/reference/reference.html#tmpdir [1]

• Require Python >=3.8.1

  The motivation here is to bring in a new version of flake8, which has
  similar version constraints[1]. Python 3.8.0 is very old (and Python 3.8
  is EoL anyway)

  Link: PyCQA/flake8@aa002ee [1]

• Update pytest

  There was one new error:

    TypeError: exceptions must be derived from Warning, not <class 'NoneType'>
  

  Fix this following the docs[1]

  Link: https://docs.pytest.org/en/8.3.x/how-to/capture-warnings.html#additional-use-cases-of-warnings-in-tests [1]

• Update black

  Also some fixes for 5b74aba

  • loosen the version constraint
  • restore the --check flag to the lint script

• Update flake8

  This required fixes an error in the config (I also updated the relevant
  link, the old one would 404):

    ValueError: Error code '#' supplied to 'extend-ignore' option does not match '^[A-Z]{1,3}[0-9]{0,3}$'
  

  And some errors in the code:

    isort/literal.py:59:8: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
    tests/unit/test_isort.py:13:1: F401 'typing.Dict' imported but unused
  

  The second test conflicted with mypy, since Dict was only used in
  commented annotations, to make them both happy move one of these
  annotations out of a comment (in the future we should probably move all
  such annotations out of comments)

• Update hypothesis

  This required addressing some errors from mypy:

    tests/integration/test_setting_combinations.py:20: error: "SearchStrategy" expects no type arguments, but 1 given  [type-arg]
    tests/integration/test_hypothesmith.py:36: error: "SearchStrategy" expects no type arguments, but 1 given  [type-arg]