[android] Use contextlib_ext.Optional for conditional context managers.

build/android/PRESUBMIT.py

 # Copyright (c) 2013 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.
 
 """Presubmit script for android buildbot.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into depot_tools.
 """
 
@@ skipping 14 matching lines @@
   output.extend(input_api.canned_checks.RunPylint(
       input_api,
       output_api,
       pylintrc='pylintrc',
       black_list=build_pys,
       extra_paths_list=[
           J(),
           J('gyp'),
           J('buildbot'),
           J('..', '..', 'third_party', 'catapult', 'common', 'py_trace_event'),
+          J('..', '..', 'third_party', 'catapult', 'common', 'py_utils'),
           J('..', '..', 'third_party', 'catapult', 'devil'),
           J('..', '..', 'third_party', 'catapult', 'tracing')
       ]))
   output.extend(input_api.canned_checks.RunPylint(
       input_api,
       output_api,
       white_list=build_pys,
       extra_paths_list=[J('gyp'), J('gn')]))
 
   # Disabled due to http://crbug.com/410936
@@ skipping 27 matching lines @@
 
   return output
 
 
 def CheckChangeOnUpload(input_api, output_api):
   return CommonChecks(input_api, output_api)
 
 
 def CheckChangeOnCommit(input_api, output_api):
   return CommonChecks(input_api, output_api)