Additional improvements to install scripts

visual_studio/NativeClientVSAddIn/InstallerResources/install.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Copies necessary add-in files into place to install the add-in.
 
 This script will copy the necessary files for the Visual Studio add-in
 to where Visual Studio can find them. It assumes the current directory
 contains the necessary files to copy.
 """
 
 import os
 import platform
 import shutil
 
 def main():
   if platform.system() != 'Windows':
     raise Exception('Must install to Windows system')
 
   # Ensure environment variables are set
-  nacl_sdk_root = os.path.expandvars('%NACL_SDK_ROOT%', None)
-  chrome_path = os.path.expandvars('%CHROME_PATH%', None)
-  if nacl_sdk_root == None:
+  nacl_sdk_root = os.getenv('NACL_SDK_ROOT', None)
+  chrome_path = os.getenv('CHROME_PATH', None)
+  if nacl_sdk_root is None:
     raise Exception('Environment Variable NACL_SDK_ROOT is not set')
-  if chrome_path == None:
+  if chrome_path is None:
     raise Exception('Environment Variable CHROME_PATH is not set')
 
   # Copy the necessary files into place
-  addInDir = os.path.expandvars(
+  add_in_directory = os.path.expandvars(
     '%USERPROFILE%\My Documents\Visual Studio 2010\Addins')
-  shutil.copy('./NativeClientVSAddIn.AddIn', addInDir)
-  shutil.copy('./NativeClientVSAddIn.dll', addInDir)
+  shutil.copy('./NativeClientVSAddIn.AddIn', add_in_directory)
+  shutil.copy('./NativeClientVSAddIn.dll', add_in_directory)
 
 if __name__ == '__main__':
   main()