Handle empty or broken JSON file

[stratofax]

Currently, NISTLib will throw an exception when it tries to read an EDF that doesn't contain the expected data, but BallotMaker doesn't handle or log these exceptions.

[trustthevote]

If NISTLib is a library used by BallotMaker to ingest an EDF, then there is no need for later (running after ingestion) code to re-validate an EDF

[stratofax]

Thanks for the feedback, I realized the Issue title is misleading. I agree 100% that testing the EDF should only happen once.

The issue is that the NISTLib responds to errors in the JSON file by throwing an exception, which means that program execution is immediately halted. I'd like to set up the app so the exception will be logged and the app will exit gracefully with a message (that doesn't include a stack trace) and an error code.

However, since we are currently in complete control of the contents of any JSON data we feed to BallotMaker, there's absolutely no reason to implement this feature right now. For that reason, this issue is not tied to any milestone; instead, I'm listing it here so it doesn't fall throught the cracks.

I've updated the title with the hopefully more descriptive "Handle" verb, instead of the confusing "Test for" description.

[stratofax]

Ultimately I'd like to migrate all of the error handling to Python's exception mechanism, including the current code that handles file input errors using error codes from strerror / errno.

Applies to these modules:

• cli
• constants
• election_data