Enable invalid regex tests

Author: manycoding

jsonschema/tests/test_validators.py

@@ -910,11 +910,11 @@ def test_minItems_invalid_string(self):
             self.Validator.check_schema({"minItems": "1"})
 
 
-class TestDraft6InvalidRegex(InvalidRegexMixin, object):
+class TestDraft6InvalidRegex(InvalidRegexMixin, TestCase):
     Validator = validators.Draft6Validator
 
 
-class TestDraft7InvalidRegex(InvalidRegexMixin, object):
+class TestDraft7InvalidRegex(InvalidRegexMixin, TestCase):
     Validator = validators.Draft7Validator