Add pylint to presubmit checks

drover.py

 #!/usr/bin/python
 # Copyright (c) 2010 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 optparse
 import os
 import re
 import subprocess
 import sys
@@ skipping 384 matching lines @@
   if options.branch:
     DEFAULT_WORKING += ("_" + options.branch)
 
   if not isMinimumSVNVersion(1, 5):
     print "You need to use at least SVN version 1.5.x"
     return 1
 
   # Override the default properties if there is a drover.properties file.
   global file_pattern_
   if os.path.exists("drover.properties"):
-    f = open("drover.properties")
-    exec(f)
-    f.close()
-    if FILE_PATTERN:
-      file_pattern_ = FILE_PATTERN
+    FILE_PATTERN = file_pattern_
+    execfile("drover.properties")
+    file_pattern_ = FILE_PATTERN
 
   if options.revert and options.branch:
     url = BRANCH_URL.replace("$branch", options.branch)
   elif options.merge and options.sbranch:
     url = BRANCH_URL.replace("$branch", options.sbranch)
   else:
     url = TRUNK_URL
 
   working = options.workdir or DEFAULT_WORKING
 
@@ skipping 130 matching lines @@
 
   if options.local and (options.revert or options.branch):
     option_parser.error("--local cannot be used with --revert or --branch")
     return 1
 
   return drover(options, args)
 
 
 if __name__ == "__main__":
   sys.exit(main())