Thanks to notes from @tkimnguyen I've implemented Sentry.io on one of our sites.
I'm now seeing this error occur (maybe every two days). When I visit the page I am unable to replicate the error, hoping someone can enlighten me.
Traceback (innermost last):
Module ZPublisher.Publish, line 127, in publish
Module ZPublisher.BaseRequest, line 554, in traverse
unbound method repr() must be called with Application instance as first argument (got nothing instead)