application_structure

./
..apibase/
... admin.py
... apps.py
... models.py
... serializers.py
... tests.py
... urls.py
... views.py

.. projekt
... settings.py
... urls.py
... router.py

.. legassy
... admin.py
... apps.py
... models.py
... serializers.py
... tests.py
... urls.py
... views.py

error_output

./manage.py runserver 0.0.0.0:8000
Performing system checks...

Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x7f13fc0d4f28>
Traceback (most recent call last):
  File "/usr/local/lib/venvs/snapi/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/lib/venvs/snapi/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 125, in inner_run
    self.check(display_num_errors=True)
  File "/usr/local/lib/venvs/snapi/lib/python3.6/site-packages/django/core/management/base.py", line 405, in check
    raise SystemCheckError(msg)
django.core.management.base.SystemCheckError: SystemCheckError: System check identified some issues:

ERRORS:
apibase.User.company_id: (fields.E005) 'choices' must be an iterable containing (actual value, human readable name) tuples.

models.py

from django.db import models
from django.contrib.auth.models import AbstractUser

from legassy.models import Company

class User(AbstractUser):
    """
        Overrides the default Django user model.

        Anything specific to the usage of the user, as it pertains to
        the Django application, MUST be added here.
    """
    company_id = models.IntegerField(choices=Company.objects.all())

synopsis

I have an application, written in PHP, that is currently running in production.   I am now, utilzing python3 and Django
to write a JSON API for the application.  To do this without causing any problems, i've opted to use 2 databases.

I've overridden the default User model for Django, and attempted to add an InterField to the user model, containing 
the company_id with choices boxes containing the id and name of all the companies from database 2.  I know Django doesn't
support cross-database foreign key, so have decided an integer field will work just fine.

Just not sure how to make the choices a valid tuple for this slim usecase.