bpo-40275: Use new test.support helper submodules in tests (GH-21315)

diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 770e2c5..61b4b91 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -16,6 +16,7 @@
 import unittest
 
 import test.support
+from test.support import import_helper
 import test.string_tests
 import test.list_tests
 from test.support import bigaddrspacetest, MAX_Py_ssize_t
@@ -967,7 +968,7 @@
         self.assertEqual(c, b'hllo')
 
     def test_sq_item(self):
-        _testcapi = test.support.import_module('_testcapi')
+        _testcapi = import_helper.import_module('_testcapi')
         obj = self.type2test((42,))
         with self.assertRaises(IndexError):
             _testcapi.sequence_getitem(obj, -2)
@@ -1024,8 +1025,8 @@
 
     # Test PyBytes_FromFormat()
     def test_from_format(self):
-        ctypes = test.support.import_module('ctypes')
-        _testcapi = test.support.import_module('_testcapi')
+        ctypes = import_helper.import_module('ctypes')
+        _testcapi = import_helper.import_module('_testcapi')
         from ctypes import pythonapi, py_object
         from ctypes import (
             c_int, c_uint,