Restored support to oldest Django versions

pwa/app_settings.py

@@ -3,8 +3,9 @@ from django.conf import settings
 import os
 
 # Path to the service worker implementation.  Default implementation is empty.
-PWA_SERVICE_WORKER_PATH = getattr(settings, 'PWA_SERVICE_WORKER_PATH', 'serviceworker.js')
-
+PWA_SERVICE_WORKER_PATH = getattr(settings, 'PWA_SERVICE_WORKER_PATH',
+                                  os.path.join(os.path.abspath(os.path.dirname(__file__)), 'templates',
+                                               'serviceworker.js'))
 # App parameters to include in manifest.json and appropriate meta tags
 PWA_APP_NAME = getattr(settings, 'PWA_APP_NAME', 'MyApp')
 PWA_APP_DESCRIPTION = getattr(settings, 'PWA_APP_DESCRIPTION', 'My Progressive Web App')