misc: don't encode json in local charset in python 3 (#36515)

wcs/qommon/misc.py

@@ -499,6 +499,9 @@ class JSONEncoder(json.JSONEncoder):
 
 def json_encode_helper(d, charset):
     '''Encode a JSON structure into local charset'''
+    if six.PY3:
+        # in python 3 we keep strings, no conversion to bytes
+        return d
     if isinstance(d, unicode):
         return d.encode(charset)
     elif isinstance(d, list):