Fix presubmit check for depot_tools on linux and mac.

PRESUBMIT.py

 # Copyright (c) 2009 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.
 
 """Top-level presubmit script for depot tools.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into gcl.
 """
 
@@ skipping 40 matching lines @@
 
 def RunPylint(input_api, output_api):
   import glob
   files = glob.glob('*.py')
   # It's a python script
   files.append('git-try')
   # It uses non-standard pylint exceptions that makes pylint always fail.
   files.remove('cpplint.py')
   try:
     proc = input_api.subprocess.Popen(['pylint', '-E'] + files)
-  except WindowsError:
-    # It's windows, give up.
-    return []
+  except OSError:
+    if input_api.platform == 'win32':
+      # It's windows, give up.
+      return []
+    else:
+      return [output_api.PresubmitError(
+          'Please install pylint with "easy_install pylint"')]
   proc.communicate()
   if proc.returncode:
     return [output_api.PresubmitError('Fix pylint errors first.')]
   return []