Answer by Pynchia for ConnectionError at : You have not defined a default connection

It appears Django doesn't know how to connect to the database.

Define a default connection to the DB in settings.py

DATABASES = {
    'default' : {
        'ENGINE' : 'django_mongodb_engine',
        'NAME' : 'my_database',
        ...
        'OPTIONS' : {
            'socketTimeoutMS' : 500,
            ...
        }
    }
}