BUG: get_user_model().USERNAME_FIELD causing starting Django when using custom user model

[daronzwink]

Describe the bug
After installing 7.0.2, we are getting an error starting Django as we have Django configured to use a custom user model. Our custom user model is:

AUTH_USER_MODEL = "tenants.TenantUser"

We are receiving the following error:

Traceback (most recent call last):
File "/code/manage.py", line 32, in
main()
File "/code/manage.py", line 28, in main
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.11/site-packages/django/core/management/init.py", line 442, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.11/site-packages/django/core/management/init.py", line 416, in execute
django.setup()
File "/usr/local/lib/python3.11/site-packages/django/init.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "/usr/local/lib/python3.11/site-packages/django/apps/registry.py", line 116, in populate
app_config.import_models()
File "/usr/local/lib/python3.11/site-packages/django/apps/config.py", line 269, in import_models
self.models_module = import_module(models_module_name)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/importlib/init.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "", line 1204, in _gcd_import
File "", line 1176, in _find_and_load
File "", line 1147, in _find_and_load_unlocked
File "", line 690, in _load_unlocked
File "", line 940, in exec_module
File "", line 241, in _call_with_frames_removed
File "/code/action_manager/models.py", line 4, in
from utils.models import AbstractItemModel
File "/code/utils/models.py", line 4, in
from tenants.models.tenant import Tenant
File "/code/tenants/models/init.py", line 10, in
from .tenant_user import (
File "/code/tenants/models/tenant_user.py", line 18, in
from axes.utils import reset
File "/usr/local/lib/python3.11/site-packages/axes/utils.py", line 13, in
from axes.handlers.proxy import AxesProxyHandler
File "/usr/local/lib/python3.11/site-packages/axes/handlers/proxy.py", line 10, in
from axes.conf import settings
File "/usr/local/lib/python3.11/site-packages/axes/conf.py", line 47, in
settings, "AXES_USERNAME_FORM_FIELD", get_user_model().USERNAME_FIELD
^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/site-packages/django/contrib/auth/init.py", line 176, in get_user_model
raise ImproperlyConfigured(
django.core.exceptions.ImproperlyConfigured: AUTH_USER_MODEL refers to model 'tenants.TenantUser' that has not been installed

Just to clear up any questions, we do have our "tenants" in the Django INSTALLED_APPS and we also have our "TenantUser" model imported in the "tenants > models > __init__.py" file. Finally, we do have "USERNAME_FIELD" defined in our "TenatUser" model and it has a value of:

USERNAME_FIELD = "email"

To Reproduce
Steps to reproduce the behavior:

1. Upgrade django-axes to 7.02
2. Configure Django to use a custom model
3. There should be an error attempting to boot Django similar to the trace above.

Expected behavior
If AXES_USERNAME_FORM_FIELD is defined, it should not attempt to resolve "get_user_model().USERNAME_FIELD", which is not able to directly resolve when using a custom model in its current state.

Your environment
python version: 3.11
django version: 4.2.19
django-axes version: 7.0.2

Additional context
As soon as I downgrade to 7.0.1, everything works properly. I believe it is related to recent fix #1270

Possible implementation
Check for the existence of AXES_USERNAME_FORM_FIELD before attempting to resolve get_user_model().USERNAME_FIELD, or if attempting to resolve get_user_model().USERNAME_FIELD, ensure USERNAME_FIELD returns a valid value.

[aliceni81]

+1