Use 'force_text', not 'unicode', for compat across python version

rest_framework/fields.py

@@ -102,13 +102,13 @@ def humanize_strptime(format_string):
 
 def strip_multiple_choice_msg(help_text):
     """
-    Remove the 'Hold down "control" ...' message that is enforced in select
-    multiple fields.
+    Remove the 'Hold down "control" ...' message that is Django enforces in
+    select multiple fields on ModelForms.  (Required for 1.5 and earlier)
 
     See https://code.djangoproject.com/ticket/9321
     """
     multiple_choice_msg = _(' Hold down "Control", or "Command" on a Mac, to select more than one.')
-    multiple_choice_msg = unicode(multiple_choice_msg)
+    multiple_choice_msg = force_text(multiple_choice_msg)
 
     return help_text.replace(multiple_choice_msg, '')
 

rest_framework/tests/test_serializer.py

@@ -1385,7 +1385,7 @@ class ManyFieldHelpTextTest(TestCase):
         message that Django appends to choice fields.
         """
         rel_field = fields.Field(help_text=ManyToManyModel._meta.get_field('rel').help_text)
-        self.assertEqual('Some help text.', unicode(rel_field.help_text))
+        self.assertEqual('Some help text.', rel_field.help_text)
 
 
 class AttributeMappingOnAutogeneratedFieldsTests(TestCase):