[Telemetry] Reduce misleading spam in unittest output.

tools/telemetry/telemetry/page/page_measurement_unittest_base.py

Index: tools/telemetry/telemetry/page/page_measurement_unittest_base.py
diff --git a/tools/telemetry/telemetry/page/page_measurement_unittest_base.py b/tools/telemetry/telemetry/page/page_measurement_unittest_base.py
index 3898435cd6104a05b9151dc8f770ec24e6046479..76c98d185152652be22f7f7c2ba992371562baeb 100644
--- a/tools/telemetry/telemetry/page/page_measurement_unittest_base.py
+++ b/tools/telemetry/telemetry/page/page_measurement_unittest_base.py
@@ -4,6 +4,7 @@
 
 import unittest
 
+from telemetry.core import exceptions
 from telemetry.core import util
 from telemetry.page import page_runner
 from telemetry.page import page as page_module
@@ -22,6 +23,7 @@ class BasicTestPage(page_module.Page):
   def RunSmoothness(self, action_runner):
     action_runner.RunAction(ScrollAction())
 
+
 class PageMeasurementUnitTestBase(unittest.TestCase):
   """unittest.TestCase-derived class to help in the construction of unit tests
   for a measurement."""
@@ -77,7 +79,7 @@ class PageMeasurementUnitTestBase(unittest.TestCase):
         def FakeStartTracing(*args, **kwargs):
           ActualStartTracing(*args, **kwargs)
           start_tracing_called[0] = True
-          raise Exception('Intentional exception')
+          raise exceptions.IntentionalException
         browser.StartTracing = FakeStartTracing
 
         ActualStopTracing = browser.StopTracing