Fix bug detecting s3 not found error
Fix bug detecting s3 not found error

Summary: Missing parens around a boolean expression caused a nil-pointer panic.

Reviewers: O1553 Project kraken: Add blocking reviewers, yiran, evelynl

Reviewed By: O1553 Project kraken: Add blocking reviewers, yiran, evelynl

Subscribers: jenkins

Differential Revision: https://code.uberinternal.com/D2203109

uber/kraken,uber/kraken,uber/kraken,uber/kraken,uber/kraken