[Telemetry] Makes serially_executed_browser_test_case.LoadAllTestsInModule return nothing if not ex…

telemetry/telemetry/testing/serially_executed_browser_test_case.py

Index: telemetry/telemetry/testing/serially_executed_browser_test_case.py
diff --git a/telemetry/telemetry/testing/serially_executed_browser_test_case.py b/telemetry/telemetry/testing/serially_executed_browser_test_case.py
index db421d0059dd8caadcdc42101620531a3ab9a6e9..3a469cb3cfdd9ee49c86b43efab8d7df81c9f906 100644
--- a/telemetry/telemetry/testing/serially_executed_browser_test_case.py
+++ b/telemetry/telemetry/testing/serially_executed_browser_test_case.py
@@ -142,11 +142,14 @@ def LoadAllTestsInModule(module):
     test cases to be run.
   """
   suite = unittest.TestSuite()
+  finder_options = options_for_unittests.GetCopy()
+  if not hasattr(finder_options, 'browser_test_runner_running'):
+    return suite
   for _, obj in inspect.getmembers(module):
     if (inspect.isclass(obj) and
         issubclass(obj, SeriallyExecutedBrowserTestCase)):
       for test in GenerateTestCases(
-          test_class=obj, finder_options=options_for_unittests.GetCopy()):
+          test_class=obj, finder_options=finder_options):
         suite.addTest(test)
   return suite