Auto strip trailing whitespace in Python modules

--HG--
extra : amend_source : 5e2c413a7e9ce3c04bb86abf5254631db449d443

ftplugin/python.vim

@@ -5,3 +5,8 @@ setlocal expandtab
 setlocal autoindent
 setlocal smartindent
 setlocal cinwords=if,elif,else,for,while,try,except,finally,def,class
+if !exists("stripwhitespace_autocommand")
+  let stripwhitespace_autocommand = 1
+  aug stripwhitespace
+  autocmd stripwhitespace BufWritePre <buffer> %s/\s\+$//e
+endif