Upgrading to OppiaMobile Server v0.12.3

Update packages

There are updated packages in this release:

1. Run: (env)$ pip install -r requirements.txt

Update database

1. Run: (env)$ python manage.py migrate

settings_secret.py changes

If you are hosting on Amazon Web Services, you can configure django-ses for sending emails. See: https://github.com/django-ses/django-ses