Copied files from depot_tools.

testing_support/auto_stub.py

Index: testing_support/auto_stub.py
diff --git a/testing_support/auto_stub.py b/testing_support/auto_stub.py
index 91a67af62d26013c41a8c128ee8d17e415d7f9e7..71970a52323a82f477c016effdda510806aa2909 100644
--- a/testing_support/auto_stub.py
+++ b/testing_support/auto_stub.py
@@ -34,6 +34,9 @@ class SimpleMock(object):
   def __init__(self, unit_test):
     """Do not call __init__ if you want to use the global call list to detect
     ordering across different instances.
+
+    Args:
+      unit_test (unittest.TestCase): instance of a test class.
     """
     self.calls = []
     self.unit_test = unit_test