Fix missing import statement.

server/site_tests/suites/control.network_wifi

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 AUTHOR = "Chrome OS Team"
 TIME = "LONG"
 NAME = "NetworkWiFi"
 TEST_CATEGORY = "Stress"
 TEST_CLASS = "suite"
 TEST_TYPE = "server"
@@ skipping 10 matching lines @@
 
 server     - the IP address of the server (automatically filled in)
 client     - the IP address of the client (automatically filled in)
 router     - the IP address of the WiFi AP/Router and the names of the
              wifi and wired devices to configure
 """
 
 import os
 import time
 
+from autotest_lib.client.common_lib import error
 from autotest_lib.server import site_host_attributes, site_remote_power
 from autotest_lib.server import site_wifitest
 from autotest_lib.server.hosts import ssh_host
 
 
 # Time in seconds to leave power off during power cycle.
 POWER_CYCLE_TIME_SECS = 1
 
 # Timeout in seconds for waiting for APs to come back from power cycle.
 POWER_CYCLE_TIMEOUT_SECS = 120
@@ skipping 34 matching lines @@
                            'cycle.')
 
   args.append('router_addr=' + str(client_attributes.router_addr))
   args.append('server_addr=' + str(client_attributes.server_addr))
 
   site_wifitest.run_test_dir('network_WiFiSecMat', job, args, machine)
   site_wifitest.run_test_dir('network_WiFiMatFunc', job, args, machine)
 
 
 parallel_simple(run_server_tests, machines)