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

build/android/pylib/__init__.py

 # Copyright (c) 2012 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.
 
 import os
 import sys
 
 
 _CATAPULT_PATH = os.path.abspath(os.path.join(
     os.path.dirname(__file__), '..', '..', '..', 'third_party', 'catapult'))
 
 _DEVIL_PATH = os.path.join(_CATAPULT_PATH, 'devil')
 
 _PYTRACE_PATH = os.path.join(_CATAPULT_PATH, 'common', 'py_trace_event')
 
+_PY_UTILS_PATH = os.path.join(_CATAPULT_PATH, 'common', 'py_utils')
+
 _TRACE2HTML_PATH = os.path.join(_CATAPULT_PATH, 'tracing')
 
+
 if _DEVIL_PATH not in sys.path:
   sys.path.append(_DEVIL_PATH)
 
 if _PYTRACE_PATH not in sys.path:
   sys.path.append(_PYTRACE_PATH)
 
+if _PY_UTILS_PATH not in sys.path:
+  sys.path.append(_PY_UTILS_PATH)
+
 if _TRACE2HTML_PATH not in sys.path:
   sys.path.append(_TRACE2HTML_PATH)