Django подтягивает настройки из global_settings.py, а не из core.settings.py
manage.py
def main():
"""Run administrative tasks."""
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'core.settings')
FAILED tests/test_api.py::test_settings - AttributeError: module 'django.conf.global_settings' has no attribute 'ROOT_URLCONF'