Django 1.7 upgrade error: AppRegistryNotReady: Models aren't loaded yet

Question

I am trying to upgrade a project from Django 1.6 to 1.7. So far, I have created a new virtualenv with all the same installs and upgraded the Django version to the new release. I need to upgrade from South, but had errors doing so, so I thought I'll initially just try runserver, and I get the following error:

Traceback (most recent call last):
      File "manage.py", line 10, in <module>
        execute_from_command_line(sys.argv)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
        utility.execute()
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/core/management/__init__.py", line 354, in execute
        django.setup()
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/__init__.py", line 21, in setup
        apps.populate(settings.INSTALLED_APPS)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate
        app_config.import_models(all_models)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/apps/config.py", line 197, in import_models
        self.models_module = import_module(models_module_name)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
        __import__(name)
      File "/Users/Name/Dev/tps/products/models.py", line 127, in <module>
        watson.register(Product.objects.exclude(productimage=None))
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/manager.py", line 92, in manager_method
        return getattr(self.get_queryset(), name)(*args, **kwargs)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/query.py", line 698, in exclude
        return self._filter_or_exclude(True, *args, **kwargs)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/query.py", line 707, in _filter_or_exclude
        clone.query.add_q(~Q(*args, **kwargs))
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1287, in add_q
        clause, require_inner = self._add_q(where_part, self.used_aliases)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1314, in _add_q
        current_negated=current_negated, connector=connector)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1138, in build_filter
        lookups, parts, reffed_aggregate = self.solve_lookup_type(arg)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1076, in solve_lookup_type
        _, field, _, lookup_parts = self.names_to_path(lookup_splitted, self.get_meta())
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1339, in names_to_path
        field, model, direct, m2m = opts.get_field_by_name(name)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/options.py", line 416, in get_field_by_name
        cache = self.init_name_map()
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/options.py", line 445, in init_name_map
        for f, model in self.get_all_related_m2m_objects_with_model():
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/options.py", line 563, in get_all_related_m2m_objects_with_model
        cache = self._fill_related_many_to_many_cache()
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/db/models/options.py", line 577, in _fill_related_many_to_many_cache
        for klass in self.apps.get_models():
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/utils/lru_cache.py", line 101, in wrapper
        result = user_function(*args, **kwds)
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/apps/registry.py", line 168, in get_models
        self.check_models_ready()
      File "/Users/Name/.virtualenvs/test17/lib/python2.7/site-packages/django/apps/registry.py", line 131, in check_models_ready
        raise AppRegistryNotReady("Models aren't loaded yet.")
    django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

Any ideas what might be causing the error and how to fix it?

Answer 1

The problem is with this line ("/Users/Name/Dev/tps/products/models.py", line 127):

watson.register(Product.objects.exclude(productimage=None))

You try to reference a model at the import time. It is no longer possible in Django 1.7. Django 1.7 allows you to use your models only after all of the applications are loaded. You should move this call to the ready callback of AppConfig, like this:

from django.apps import AppConfig


class ProductsConfig(AppConfig):
    name = 'products'

    def ready(self):
        Product = self.get_model('Product')
        watson.register(Product.objects.exclude(productimage=None))

Then you should reference this AppConfig in the __init__.py of your products app:

default_app_config = 'products.apps.ProductsConfig'

Where apps is the name of the module where you put the config.

Relevant Django doc: https://docs.djangoproject.com/en/dev/ref/applications/

Overall, because of this change, migrating to Django 1.7 is not as easy as one would like it to be. Here are some troubleshooting tips: https://docs.djangoproject.com/en/1.7/ref/applications/#troubleshooting