Additional improvements to install scripts

visual_studio/NativeClientVSAddIn/InstallerResources/install.py

Index: visual_studio/NativeClientVSAddIn/InstallerResources/install.py
diff --git a/visual_studio/NativeClientVSAddIn/InstallerResources/install.py b/visual_studio/NativeClientVSAddIn/InstallerResources/install.py
index a4fead53e9c42e09c2b69c1f63e71962f15000cf..5ce7c666ce3339fca493ea476aa482abf4d19fbd 100644
--- a/visual_studio/NativeClientVSAddIn/InstallerResources/install.py
+++ b/visual_studio/NativeClientVSAddIn/InstallerResources/install.py
@@ -19,18 +19,18 @@ def main():
     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()