To comply with what's coming.

rohe · rohe · commit f015a181f188 · 2019-03-06T09:27:35.000+01:00
diff --git a/src/oidcmsg/message.py b/src/oidcmsg/message.py
@@ -2,7 +2,7 @@
 import copy
 import json
 import logging
-from collections import MutableMapping
+from collections.abc import MutableMapping
 from urllib.parse import parse_qs
 from urllib.parse import urlencode
 
