[Android] Add a configurable environment for devil/.

build/android/devil/android/battery_utils_test.py

Index: build/android/devil/android/battery_utils_test.py
diff --git a/build/android/devil/android/battery_utils_test.py b/build/android/devil/android/battery_utils_test.py
index 64253a526c598d677c402516e6e8d02173d38a78..7057bcd2c086121c5a8a80a9feca894cc5700829 100755
--- a/build/android/devil/android/battery_utils_test.py
+++ b/build/android/devil/android/battery_utils_test.py
@@ -10,19 +10,17 @@ Unit tests for the contents of battery_utils.py
 # pylint: disable=protected-access,unused-argument
 
 import logging
-import os
 import sys
 import unittest
 
+from devil import devil_env
 from devil.android import battery_utils
 from devil.android import device_errors
 from devil.android import device_utils
 from devil.android import device_utils_test
 from devil.utils import mock_calls
-from pylib import constants
 
-sys.path.append(os.path.join(
-    constants.DIR_SOURCE_ROOT, 'third_party', 'pymock'))
+sys.path.append(devil_env.config.pymock_path)
 import mock # pylint: disable=F0401
 
 _DUMPSYS_OUTPUT = [