Replace customzied test failure assertion with ResultReasonRE from engine

This change is to facilitate the annotation protocol -> luciexe protocol
migration in the future. The failure response structure will be changed
after the migration. Therefore, we only need to change the
implementation detail of ResultReasonRE at that time.

R=iannucci

Change-Id: If5e0005dddcaf6ccdfbcb047e3855763cf4eadc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2146066
Auto-Submit: Yiwei Zhang <yiwzhang@google.com>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

recipes/recipe_modules/gclient/tests/sync_failure.py

@@ -14,9 +14,7 @@ def GenTests(api):
   yield api.test(
       'no-json',
       api.override_step_data('gclient sync', retcode=1),
-      api.post_check(
-          lambda check, steps:
-          check(not steps['$result']['failure']['humanReason']
-                .startswith('Uncaught Exception'))),
+      # Should not fail with uncaught exception
+      api.post_process(post_process.ResultReasonRE, r'^(?!Uncaught Exception)'),
       api.post_process(post_process.DropExpectation)
   )