Include exception information when warning about a coverage parse failure
Include exception information when warning about a coverage parse failure

Summary:
We have numerous reports of "Empty file" in our error logs, and it'd be nice to
have a stack trace with locals.

Test Plan: None

Reviewers: treaster

Reviewed By: treaster

Subscribers: changesbot

Differential Revision: https://tails.corp.dropbox.com/D193814

dropbox/changes,dropbox/changes,dropbox/changes,dropbox/changes