[3.12] gh-107909: Test explicit object base in PEP695 generic class…

…es (GH-108001) (#108022)

gh-107909: Test explicit `object` base in PEP695 generic classes (GH-108001)
(cherry picked from commit b61f599)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Lib/test/test_type_params.py

@@ -148,6 +148,10 @@ def test_disallowed_expressions(self):
         check_syntax_error(self, "def f[T: [(x := 3) for _ in range(2)]](): pass")
         check_syntax_error(self, "type T = [(x := 3) for _ in range(2)]")
 
+    def test_incorrect_mro_explicit_object(self):
+        with self.assertRaisesRegex(TypeError, r"\(MRO\) for bases object, Generic"):
+            class My[X](object): ...
+
 
 class TypeParamsNonlocalTest(unittest.TestCase):
     def test_nonlocal_disallowed_01(self):