"/cohorts/" route does not work on test or production

[ssciolla]

The cohort list, which uses the /cohorts/ route, does not seem to be accessible on either the AWS test instance or on-premises production instance of Student Explorer. I was seeing the following error when trying to access the route on the former:

NoReverseMatch at /cohorts/
Reverse for 'cohort' with arguments '('',)' not found. 1 pattern(s) tried: ['cohorts/(?P<code>[\\s\\w-]+)/$']

There does not seem to be a problem with this route (which uses CohortView) when running the application locally.