Fix override_settings compat for 1.6

Author: Ryan P Kilby

rest_framework_filters/tests.py

@@ -8,14 +8,20 @@
 from django.utils.dateparse import parse_time, parse_datetime
 
 from django.db import models
-from django.test import TestCase, override_settings
+from django.test import TestCase
 from django.contrib.auth.models import User
 
 from . import filters
 from .filters import RelatedFilter, AllLookupsFilter
 from .filterset import FilterSet
 from .backends import DjangoFilterBackend
 
+try:
+    from django.test import override_settings
+except ImportError:
+    # TODO: Remove this once Django 1.6 is EOL.
+    from django.test.utils import override_settings
+
 
 class Note(models.Model):
     title = models.CharField(max_length=100)