fix pylint warnings

native_client_sdk/src/build_tools/build_updater.py

Index: native_client_sdk/src/build_tools/build_updater.py
diff --git a/native_client_sdk/src/build_tools/build_updater.py b/native_client_sdk/src/build_tools/build_updater.py
index efe610a40b36ab28b0ebedfc2852484a26751f4c..8283790d0990c350cd87832b19b6dddfecd58a80 100755
--- a/native_client_sdk/src/build_tools/build_updater.py
+++ b/native_client_sdk/src/build_tools/build_updater.py
@@ -11,10 +11,8 @@ tool users run to download new bundles, update existing bundles, etc.
 
 import buildbot_common
 import build_utils
-import cStringIO
 import optparse
 import os
-import re
 import sys
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
@@ -111,9 +109,9 @@ def UpdateRevisionNumber(out_dir, revision_number):
   SDK_UPDATE_MAIN = os.path.join(out_dir,
       'nacl_sdk/sdk_tools/sdk_update_main.py')
 
-  file = open(SDK_UPDATE_MAIN, 'r').read().replace(
+  contents = open(SDK_UPDATE_MAIN, 'r').read().replace(
       '{REVISION}', str(revision_number))
-  open(SDK_UPDATE_MAIN, 'w').write(file)
+  open(SDK_UPDATE_MAIN, 'w').write(contents)
 
 
 def BuildUpdater(out_dir, revision_number=None):
@@ -131,7 +129,7 @@ def BuildUpdater(out_dir, revision_number=None):
   buildbot_common.RemoveDir(os.path.join(out_dir, 'nacl_sdk'))
 
   updater_files = MakeUpdaterFilesAbsolute(out_dir)
-  out_files = [out_file for in_file, out_file in updater_files]
+  out_files = [out_file for _, out_file in updater_files]
 
   CopyFiles(updater_files)
   UpdateRevisionNumber(out_dir, revision_number)