Fix a typo that resulted in no tests to be run in depot_tools. :(

tests/super_mox.py

 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Simplify unit tests based on pymox."""
 
 import os
 import random
 import shutil
 import string
@@ skipping 123 matching lines @@
     TestCaseUtils.tearDown(self)
     mox.MoxTestBase.tearDown(self)
 
   def MockList(self, parent, items_to_mock):
     for item in items_to_mock:
       # Skip over items not present because of OS-specific implementation,
       # implemented only in later python version, etc.
       if hasattr(parent, item):
         try:
           self.mox.StubOutWithMock(parent, item)
-        except TypeError:
-          raise TypeError('Couldn\'t mock %s in %s' % (item, parent.__name__))
+        except TypeError, e:
+          raise TypeError(
+              'Couldn\'t mock %s in %s: %s' % (item, parent.__name__, e))
 
   def UnMock(self, obj, name):
     """Restore an object inside a test."""
     for (parent, old_child, child_name) in self.mox.stubs.cache:
       if parent == obj and child_name == name:
         setattr(parent, child_name, old_child)
         break