Fix tests for Python 3.11 and 3.12

Fixes #401.

Author: nicoddemus

tests/test_pytest_mock.py

@@ -246,9 +246,8 @@ def __test_failure_message(self, mocker: MockerFixture, **kwargs: Any) -> None:
             msg = "Expected call: {0}()\nNot called"
         expected_message = msg.format(expected_name)
         stub = mocker.stub(**kwargs)
-        with pytest.raises(AssertionError) as exc_info:
+        with pytest.raises(AssertionError, match=re.escape(expected_message)) as exc_info:
             stub.assert_called_with()
-        assert str(exc_info.value) == expected_message
 
     def test_failure_message_with_no_name(self, mocker: MagicMock) -> None:
         self.__test_failure_message(mocker)