Allow None to be highlighted differently

syntax/python.vim

   syn keyword pythonImport      as
   syn match   pythonFunction    "[a-zA-Z_][a-zA-Z0-9_]*" display contained
 else
-  syn keyword pythonStatement   as nonlocal None
+  syn keyword pythonStatement   as nonlocal
+  syn keyword pythonNone        None
   syn match   pythonStatement   "\<yield\s\+from\>" display
   syn keyword pythonBoolean     True False
   syn match   pythonFunction    "\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*" display contained
 
 if s:Enabled("g:python_highlight_builtin_objs")
   if s:Python2Syntax()
-    syn keyword pythonBuiltinObj	None
+    syn keyword pythonNone	        None
     syn keyword pythonBoolean		True False
   endif
   syn keyword pythonBuiltinObj	Ellipsis NotImplemented
     HiLink pythonUniRawString       String
     HiLink pythonUniRawEscape       Special
     HiLink pythonUniRawEscapeError  Error
+    HiLink pythonNone               pythonBuiltinObj
   else
     HiLink pythonBytes              String
     HiLink pythonRawBytes           String
     HiLink pythonBytesError         Error
     HiLink pythonBytesEscape        Special
     HiLink pythonBytesEscapeError   Error
+    HiLink pythonNone               pythonStatement
   endif
 
   HiLink pythonStrFormatting    Special