Allow using django-nose without setting DATABASES

[robgolding]

The DjangoSetUpPlugin calls self.runner.setup_databases(), which fails if settings.DATABASES is not set. You shouldn't be required to have a database configured to use django-nose, so perhaps this should only happen if one is in use.

[fvieira]

Agree. We use Cassandra in our project instead of an SQL database which means we don't use settings.DATABASES, and this behaviour is preventing us from using this app.

[schmitch]

Also you can't use in-memory SQL databases at the moment

django.core.exceptions.ImproperlyConfigured: settings.DATABASES is improperly configured. Please supply the NAME value.

That sucks

[jwhitlock]

There has been a lot of work in the Django side of things in django/test/runner.py setup_databases(), which may not be reflected in the django-nose version. This might include allowing an empty settings.DATABASES. I'm still using PostgreSQL, so I'm not familiar with this world. PR welcome.

Does an in-memory SQLite database let you get around it?

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': ':memory:',
    }
}