ExceptionHandlingMiddleware prevents further handling of exceptions

[jeremystretch]

Issue type

[ ] Feature request
[x] Bug report
[ ] Documentation
[ ] Housekeeping

Environment

• Python version: 3.5.2
• NetBox version: 2.3.6

Description

NetBox employs custom middleware to help process exceptions and return custom error messages in response to some common problems (e.g. incorrect file system permissions). This middleware consumes all exceptions and renders the 500 response template directly. This prevents further processing of exceptions by log handlers such as AdminEmailHandler.

ExceptionHandlingMiddleware should be adapted so that it returns a response only if we want to render a custom error message.