commit 28a6cfaefc41a4e4bfa6dd0b54318c0465987652
author Benjamin Peterson <benjamin@python.org> Tue Aug 28 17:55:35 2012 -0400
committer Benjamin Peterson <benjamin@python.org> Tue Aug 28 17:55:35 2012 -0400
tree b3334773d534a57edf85e637c30e2c07ce53f3b6
parent 2412c93a6068221686397c26b129215eac024e9c

use the stricter PyMapping_Check (closes #15801)

Objects/unicodeobject.c

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index b25b17b..8b782b4 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -9504,8 +9504,7 @@
         arglen = -1;
         argidx = -2;
     }
-    if (Py_TYPE(args)->tp_as_mapping && !PyTuple_Check(args) &&
-        !PyUnicode_Check(args))
+    if (PyMapping_Check(args) && !PyTuple_Check(args) && !PyUnicode_Check(args))
         dict = args;
 
     while (--fmtcnt >= 0) {