django/django — pull request #1582 by rca (2013-09-06 22:35:17+00:00)
Title: 12756 missing yaml module serializer error message

Running dumpdata without `pyyaml` installed will produce a useful error message:

```
[berto@scratch]$ python manage.py dumpdata --format=yaml
CommandError: Unable to serialize database: No module named yaml
```