Position-less argument specifiers were not added until python 2.7. Specify the position to fix support for older versions of python.

tschieggm · tschieggm · commit a140ef6d6003 · 2013-09-11T16:52:45.000-04:00
diff --git a/twilio/rest/resources/base.py b/twilio/rest/resources/base.py
@@ -202,7 +202,7 @@ def delete_instance(self):
         return self.parent.delete(self.name)
 
     def __str__(self):
-        return "<{} {}>".format(self.__class__.__name__, self.name[0:5])
+        return "<{0} {1}>".format(self.__class__.__name__, self.name[0:5])
 
 
 class ListResource(Resource):
@@ -321,4 +321,4 @@ def load_instance(self, data):
         return instance
 
     def __str__(self):
-        return '<{} ({})>'.format(self.__class__.__name__, self.count())
+        return '<{0} ({1})>'.format(self.__class__.__name__, self.count())
