Tests: Disable testing for apns service plugin

The `apns` package is not ready for Python3.

Author: amotl

tests/services/test_apns.py

@@ -3,9 +3,13 @@
 from unittest import mock
 from unittest.mock import call
 
+import pytest
+
 from mqttwarn.model import ProcessorItem as Item
 from mqttwarn.util import load_module_from_file
 
+pytest.skip(reason="The `apns` package is not ready for Python3", allow_module_level=True)
+
 
 @mock.patch("apns.APNs", create=True)
 @mock.patch("apns.Payload", create=True)