Make device serial required in AdbWrapper/DeviceUtils

build/android/pylib/device/adb_wrapper.py

 # Copyright 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.
 
 """This module wraps Android's adb tool.
 
 This is a thin wrapper around the adb interface. Any additional complexity
 should be delegated to a higher level (ex. DeviceUtils).
 """
 
@@ skipping 26 matching lines @@
 
 class AdbWrapper(object):
   """A wrapper around a local Android Debug Bridge executable."""
 
   def __init__(self, device_serial):
     """Initializes the AdbWrapper.
 
     Args:
       device_serial: The device serial number as a string.
     """
+    if not device_serial:
+      raise ValueError('A device serial must be specified')
     self._device_serial = str(device_serial)
 
   # pylint: disable=unused-argument
   @classmethod
   @decorators.WithTimeoutAndRetries
   def _RunAdbCmd(cls, args, timeout=None, retries=None, device_serial=None,
                  check_error=True):
     cmd = [constants.GetAdbPath()]
     if device_serial is not None:
       cmd.extend(['-s', device_serial])
@@ skipping 337 matching lines @@
     """Restarts the adbd daemon with root permissions, if possible.
 
     Args:
       timeout: (optional) Timeout per try in seconds.
       retries: (optional) Number of retries to attempt.
     """
     output = self._RunDeviceAdbCmd(['root'], timeout, retries)
     if 'cannot' in output:
       raise device_errors.AdbCommandFailedError(
           ['root'], output, device_serial=self._device_serial)