django - PostgreSQL & Heroku - cannot connect to the database -

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i'm trying add column table via django app south keep getting following error upon running python manage.py migrate <app name> command:

conn = _connect(dsn, connection_factory=connection_factory, async=async) psycopg2.operationalerror: not translate host name "ec2-107-21-99-105.comp ute-1.amazonaws.com" address: temporary failure in name resolution

does have idea why happening? i'm newbie both south , postgresql database management system (which heroku uses), more bit confused.

make sure have defined default database in settings.py this:

databases = {     'default': dj_database_url.config(default=os.environ.get('database_url')) }

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