Separate json parsing error from expansion failure in CollectionArtifactHandler
Separate json parsing error from expansion failure in CollectionArtifactHandler

Summary: - Gives better Sentry error messages.

Test Plan: None

Reviewers: paulruan, kylec

Reviewed By: kylec

Subscribers: changesbot

Differential Revision: https://tails.corp.dropbox.com/D157322

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