remove future imports (#6050)

tests/access_tests.py

@@ -1,10 +1,5 @@
 # -*- coding: utf-8 -*-
 """Unit tests for Superset"""
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
-
 import json
 import unittest