* Switch to pytest.raises().
* Add matches= to broad pytest.raises().
* Adjust the test_nonserializable_object() regex for Python <= 3.11.
* Adjust the test_nonserializable_object() regex for PyPy.
* Adjust other test exception regexes for PyPy.
* Cleanup.
* put flake8 options into separate file to remove pytest warnings
* remove ResourceLeaked warning in pypy
* suppress warnings from twisted
* ignore deprecation warnings here
* ignore deprecation warning in tests of deprecated methods
* ignore deprecation warnings here
* update test classes
* don`t use deprecated method call
* ignore deprecation warnings here
* proper warning class
* more selective ignoring
* Revert "don`t use deprecated method call"
This reverts commit 59216ab560.