If, like me, right after Open edX platform update you incour in some error, the cause could be the mysql database not synced with the new models.
The command to launch is the following (from a sudo privileged user):
cd /edx/app/edxapp/edx-platform sudo -u www-data /edx/bin/python.edxapp ./manage.py lms --settings aws syncdb --migrate
The last command will trigger south database sync process. The
–migrate, in my case, was mandatory.