retrace: Add a catch-all clause to report all errors With that running the a batch of tests from an external script can bail out early when a trace fails. Bug: angleproject:7800 Change-Id: I5041e863a8cdc212b7057b88e3f0fd68a5115470 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3990621 Commit-Queue: Gert Wollny <gert.wollny@collabora.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>