Authentication raises a 500 when the token is created (during first login)

There appears to be a bug in drf when creating tokens (in Python 3)

The issue is mentioned in https://github.com/tomchristie/django-rest-framework/pull/1382

The error in sentry is http://sentry.incuna.com/default/bydureon-epatientincunatestingcom/group/45/

We could fix this in this app but it would be better to get it fixed in drf.