Use relative imports and __init__.py in the statschannel test

This is in preparation for automatic import sorting.

bin/tests/system/statschannel/__init__.py

@@ -0,0 +1,15 @@
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+
+import pytest
+
+pytest.register_assert_rewrite("generic")

bin/tests/system/statschannel/tests_json.py

@@ -18,8 +18,7 @@ import requests
 
 import isctest.mark
 
-pytest.register_assert_rewrite("generic")
-import generic
+from . import generic
 
 pytestmark = [
     isctest.mark.with_json_c,

bin/tests/system/statschannel/tests_xml.py

@@ -19,8 +19,7 @@ import requests
 
 import isctest.mark
 
-pytest.register_assert_rewrite("generic")
-import generic
+from . import generic
 
 pytestmark = [
     isctest.mark.with_libxml2,