python3: adapt signature check for different ord() behaviour

combo/utils/signature.py

@@ -23,6 +23,7 @@ import random
 from django.conf import settings
 from django.utils.encoding import smart_bytes
 from django.utils.http import quote, urlencode
+from django.utils import six
 from django.utils.six.moves.urllib.parse import urlparse, urlunparse, parse_qs
 
 
@@ -97,8 +98,12 @@ def check_string(s, signature, keys, algo='sha256'):
             continue
         res = 0
         # constant time compare
-        for a, b in zip(signature, signature2):
-            res |= ord(a) ^ ord(b)
+        if six.PY3:
+            for a, b in zip(signature, signature2):
+                res |= a ^ b
+        else:
+            for a, b in zip(signature, signature2):
+                res |= ord(a) ^ ord(b)
         if res == 0:
             return True
     return False