Enable presubmit pylint in build/android.

build/android/pylib/base/base_test_runner.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.
 
 """Base class for running tests on a single device."""
 
-import contextlib
-import httplib
 import logging
-import os
-import tempfile
 import time
 
 from pylib import android_commands
-from pylib import constants
 from pylib import ports
 from pylib.chrome_test_server_spawner import SpawningServer
 from pylib.forwarder import Forwarder
 from pylib.valgrind_tools import CreateTool
 # TODO(frankf): Move this to pylib/utils
 import lighttpd_server
 
 
 # A file on device to store ports of net test server. The format of the file is
 # test-spawner-server-port:test-server-port
@@ skipping 148 matching lines @@
       self._spawning_server.CleanupState()
 
   def LaunchChromeTestServerSpawner(self):
     """Launches test server spawner."""
     server_ready = False
     error_msgs = []
     # TODO(pliard): deflake this function. The for loop should be removed as
     # well as IsHttpServerConnectable(). spawning_server.Start() should also
     # block until the server is ready.
     # Try 3 times to launch test spawner server.
-    for i in xrange(0, 3):
+    for _ in xrange(0, 3):
       self.test_server_spawner_port = ports.AllocateTestServerPort()
       self._ForwardPorts(
           [(self.test_server_spawner_port, self.test_server_spawner_port)])
       self._spawning_server = SpawningServer(self.test_server_spawner_port,
                                              self.adb,
                                              self.tool)
       self._spawning_server.Start()
       server_ready, error_msg = ports.IsHttpServerConnectable(
           '127.0.0.1', self.test_server_spawner_port, path='/ping',
           expected_read='ready')
       if server_ready:
         break
       else:
         error_msgs.append(error_msg)
       self._spawning_server.Stop()
       # Wait for 2 seconds then restart.
       time.sleep(2)
     if not server_ready:
       logging.error(';'.join(error_msgs))
       raise Exception('Can not start the test spawner server.')
     self._PushTestServerPortInfoToDevice()