Use set instead of Set

rest_framework/fields.py

 from __future__ import unicode_literals
-from sets import Set
 
 import collections
 import copy
@@ -1462,7 +1461,7 @@ class ListField(Field):
         """
         if html.is_html_input(data):
             data = html.parse_html_list(data)
-        if not isinstance(data, (list, tuple, Set)):
+        if not isinstance(data, (list, tuple, set)):
             self.fail('not_a_list', input_type=type(data).__name__)
         if not self.allow_empty and len(data) == 0:
             self.fail('empty')