`test_cannot_create_superuser_if_any_user_exists` is flaky

=================================== FAILURES ===================================
_______________ test_cannot_create_superuser_if_any_user_exists ________________
[gw0] linux -- Python 3.11.14 /home/runner/.cache/pypoetry/virtualenvs/flagsmith-api-h9Rv37Cj-py3.11/bin/python

admin_user = <FFAdminUser: admin@example.com>
api_client = <rest_framework.test.APIClient object at 0x7f6ac9dc2850>
mocker = <pytest_mock.plugin.MockerFixture object at 0x7f6ac9dc3350>

    def test_cannot_create_superuser_if_any_user_exists(
        admin_user: FFAdminUser, api_client: APIClient, mocker: MockerFixture
    ) -> None:
        # Given
        mocker.patch("custom_auth.serializers.is_saas", return_value=False)
    
        email = "test@example.com"
        password = FFAdminUser.objects.make_random_password()
        register_data = {
            "email": email,
            "password": password,
            "re_password": password,
            "first_name": "user",
            "last_name": "test",
            "superuser": True,
        }
        url = reverse("api-v1:custom_auth:ffadminuser-list")
    
        # When
        response = api_client.post(url, data=register_data)
    
        # Then
        assert response.status_code == status.HTTP_400_BAD_REQUEST
>       assert response.json()["superuser"] == [
            "A superuser can only be created through this  endpoint if no other users exist."
        ]
E       KeyError: 'superuser'