[Telemetry] Fix exception handling in user story runner.

tools/telemetry/telemetry/user_story/user_story_runner.py

Index: tools/telemetry/telemetry/user_story/user_story_runner.py
diff --git a/tools/telemetry/telemetry/user_story/user_story_runner.py b/tools/telemetry/telemetry/user_story/user_story_runner.py
index dfc07a2a9cffa213bc967a8384cc52269474ae50..ad9dde0be701a951390695ac1a41bdd16a52c31b 100644
--- a/tools/telemetry/telemetry/user_story/user_story_runner.py
+++ b/tools/telemetry/telemetry/user_story/user_story_runner.py
@@ -16,7 +16,6 @@ from telemetry.core import util
 from telemetry.core import wpr_modes
 from telemetry.page import page_set as page_set_module
 from telemetry.page import page_test
-from telemetry.page import shared_page_state
 from telemetry.page.actions import page_action
 from telemetry.results import results_options
 from telemetry.user_story import user_story_filter
@@ -108,6 +107,11 @@ def _RunUserStoryAndProcessErrorIfNeeded(expectations, user_story, results,
   except page_action.PageActionNotSupported as e:
     results.AddValue(
         skip.SkipValue(user_story, 'Unsupported page action: %s' % e))
+  except Exception:
+    results.AddValue(
+        failure.FailureValue(
+            user_story, sys.exc_info(), 'Unhandlable exception raised.'))
+    raise
   else:
     if expectation == 'fail':
       logging.warning(