fix : AttributeError in Python3

fix : run python weixin.py then AttributeError: 'str' object has no attribute 'decode'

weixin.py

@@ -1161,7 +1161,7 @@ class UnicodeStreamFilter:
 
     def write(self, s):
         if type(s) == str:
-            s = s.decode('utf-8')
+            s = s.encode().decode('utf-8')
         s = s.encode(self.encode_to, self.errors).decode(self.encode_to)
         self.target.write(s)