App reference in settings.py
In your `settings.py` file you need to move `juntagrico_billing` up, so it appears before `juntagrico`.
INSTALLED_APPS = (
'juntagrico_billing',
'juntagrico',
...
)
Use new URL path pattern
Update your `urls.py` to use the `path` function instead of `re_path`:
urlpatterns = [
...
path('', include('juntagrico_billing.urls')),
]