Django dumpdata will fail because of unmanaged model

[ronaldoldenburger]

When dumping data in django (manage.py dumpdata) an error will occur:

CommandError: Unable to serialize database: (1146, "Table 'xxx.django_rq_queue' doesn't exist")

This is because the django-rq has a model with managed = False, this will make Django think the table does exists, but was not created by itself.

For now ignoring the django_rq app during dumpdata will work:
./manage.py dumpdata -e django_rq

Relevant other issues: #552

[Selwin Ong]

I'd welcome a PR to fix this issue :)