tests: test_git_superproject.py: fix py3.6 & 3.7

tests/test_git_superproject.py::SuperprojectTestCase::test_Fetch was
failing in Python 3.6 and 3.7 due to attribute args only being
introduced in Python 3.8. Falling back on old way of accessing
the arguments.

Test: tox with Python 3.6 to 3.11
Change-Id: Iae1934a7bce8cbd6b4519e4dbc92d94e21b43435
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/382818
Tested-by: Daniel Kutik <daniel.kutik@lavawerk.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Daniel Kutik <daniel.kutik@lavawerk.com>
diff --git a/tests/test_git_superproject.py b/tests/test_git_superproject.py
index f884f50..dc46ec6 100644
--- a/tests/test_git_superproject.py
+++ b/tests/test_git_superproject.py
@@ -490,7 +490,9 @@
 
                     self.assertTrue(self._superproject._Fetch())
                     self.assertEqual(
-                        mock_git_command.call_args.args,
+                        # TODO: Once we require Python 3.8+,
+                        #  use 'mock_git_command.call_args.args'.
+                        mock_git_command.call_args[0],
                         (
                             None,
                             [
@@ -510,7 +512,9 @@
                     # If branch for revision exists, set as --negotiation-tip.
                     self.assertTrue(self._superproject._Fetch())
                     self.assertEqual(
-                        mock_git_command.call_args.args,
+                        # TODO: Once we require Python 3.8+,
+                        #  use 'mock_git_command.call_args.args'.
+                        mock_git_command.call_args[0],
                         (
                             None,
                             [