Add banned imports to prevent standard json import

requirements/requirements-codestyle.txt

@@ -1,5 +1,6 @@
 # PEP8 code linting, which we run on all commits.
 flake8==2.4.0
+flake8-tidy-imports==1.1.0
 pep8==1.5.7
 
 # Sort and lint imports

rest_framework/utils/encoders.py

@@ -5,7 +5,7 @@ from __future__ import absolute_import, unicode_literals
 
 import datetime
 import decimal
-import json
+import json  # noqa
 import uuid
 
 from django.db.models.query import QuerySet

rest_framework/utils/json.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import
 
 import functools
-import json
+import json  # noqa
 
 
 def strict_constant(o):

setup.cfg

@@ -6,3 +6,4 @@ license_file = LICENSE.md
 
 [flake8]
 ignore = E501
+banned-modules = json = use from rest_framework.utils import json!