Fix debug string for validateTraceCategories error.
Fix debug string for validateTraceCategories error.

Handle new metadata dict. Also add missing parenthesis.

Bug: chromium:919187
Change-Id: Id86daa13a3500d2a39418a14fb8c0ef2b52b296f
Reviewed-on: https://chromium-review.googlesource.com/c/1449696
Commit-Queue: Ben Hayden <d3ffe0e065c2328e497bb32a07f4dcb29138ef5b@chromium.org>
Reviewed-by: Ben Hayden <d3ffe0e065c2328e497bb32a07f4dcb29138ef5b@chromium.org>
Auto-Submit: Eric Seckler <d661906de75c240343b01bf83bdad954d5d7d8b2@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult