Pep8-naming

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* Formally require flake8 5.0.0 or later.
* Add support for Python 3.11.

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* Formally require Python 3.7 or later using ``python_requires``.

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* Fix warnings related to deprecated options syntax.

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* Python 3.7 or later is now required.

* ``setUpModule`` and ``tearDownModule`` are now exempted by default.

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* Fix potential stack exhaustion in the N818 check.

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* flake8 3.9.1 or later is now required.

* N818 checks exception class names for an "Error" suffix (disabled by default).

* ``asyncSetUp`` and ``asyncTearDown`` are now exempted by default.