--- a/dataimport/stores.py	Mon Nov 30 10:18:22 2015 +0100
+++ b/dataimport/stores.py	Mon Nov 30 11:09:51 2015 +0100
@@ -103,7 +103,7 @@
         and inlined relations.
         """
         entity = self._cnx.entity_from_eid(eid)
-        assert entity.cw_etype == etype, 'Trying to update with wrong type {}'.format(etype)
+        assert entity.cw_etype == etype, 'Trying to update with wrong type %s' % etype
         # XXX some inlined relations may already exists
         entity.cw_set(**kwargs)