Check that logging works when RAVEN_DSN (Sentry) not configured

[jnm]

From #170:

Fix KC logging for installations that do not use Sentry/Raven. Exception information, including tracebacks, should appear either in the uWSGI or Docker container logs (check KPI's behavior) (see kobotoolbox/kobocat@b55e48f)

Basically: if you don't use Sentry (and have RAVEN_DSN unset in your environment), and you trigger an exception, do you see the error logged anywhere? Check the log files as well as the output of docker-compose logs. If the error doesn't appear, then we have a problem with our logging setup (and probably need to file bugs against kpi and kobocat).

[noliveleger]

@jnm it does not show anything in the logs except with DEBUG is True.