how to import models to oscar.partner app's strategy module correctly?

[mat...@naturitas.es]

I have defined declared my own Strategy to Select a Stock and a price as described in http://django-oscar.readthedocs.io/en/releases-1.1/topics/prices_and_availability.html

Everything worked fine until I had the need to import a custom model class that I created in the catalogue app.

My goal was to access this custom model for the price selection strategy.  

in /apps/partner/strategy I tried to import the model like this: 

CountrySpecificProductInformation = get_model('catalogue', 'CountrySpecificProductInformation')

this call raises a Model not Registered exception:

File "/home/matyas/virtenvs/oscar/local/lib/python2.7/site-packages/oscar/core/loading.py", line 250, in get_model

  return apps.get_registered_model(app_label, model_name)

  File "/home/matyas/virtenvs/oscar/local/lib/python2.7/site-packages/django/apps/registry.py", line 260, in get_registered_model

 "Model '%s.%s' not registered." % (app_label, model_name))

  LookupError: Model 'catalogue.CountrySpecificProductInformation' not registered.

my Installed apps settings look like this: 

    INSTALLED_APPS = ['...'] +

     oscar.get_core_apps(['apps.catalogue', 'apps.promotions', 'apps.dashboard',

                                 'apps.dashboard.catalogue', 'apps.partner', 'apps.payment', 'apps.dashboard.partners',

                                 'apps.shipping', 'apps.checkout', 'apps.search'])

I am using django-oscar 1.3 with Django 1.9.9

related StackOverflow question: 

http://stackoverflow.com/questions/40214708/how-to-import-models-to-oscar-partner-apps-strategy-module-correctly

Any ideas what would be the correct approach here? 

Thank you very much,

Matyas