Fixed #7243: Corrected some example code in the custom model fields…

Fixed #7243: Corrected some example code in the custom model fields documentation. Thanks to Norman Harman for the fix.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8520 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/howto/custom-model-fields.txt

@@ -491,7 +491,7 @@ accepted lookup types to ``exact`` and ``in``::
         def get_db_prep_lookup(self, lookup_type, value):
             # We only handle 'exact' and 'in'. All others are errors.
             if lookup_type == 'exact':
-                return self.get_db_prep_value(value)
+                return [self.get_db_prep_value(value)]
             elif lookup_type == 'in':
                 return [self.get_db_prep_value(v) for v in value]
             else: