Policy error handling implemented

[danieldupriest]

Any errors that occur when accessing the policy file will now fail silently, allowing the user to view, edit and submit reports created with different policy files. The only feature that will break is rule violations. If a section has changed or no longer exists, that section's rules will simply not appear in the UI or in emailed reports. To test:

1. Ensure your .env file has the correct contents
2. Start dev server with python manage.py runserver and create a report using Postman.
3. Delete several sections of the policy file.
4. Start docker, log in, and try viewing, editing, saving, and finally submitting the old report.
5. It should act normally, except for rule violations, which will no longer appear.

[danieldupriest]

Whenever a Pipfile dependency is changed you need to rerun pipenv install. This doesn't happen too often, so normally pipenv shell will run with no problem.