On a Debian system with python2.4, if you've got the package python-json installed, then running ./manage.py dumpdata raises an error: AttributeError: 'module' object has no attribute 'JSONEncoder'. This only happens if you're using r9707 or newer though. A workaround is to remove python-json.
I see a similar error on Ubuntu (with python2.5). If you've got python-json and don't have python-simplejson installed, then you see the same error in the same conditions. Either removing python-json or installing python-simplejson fixes it in this case.
I think this is due to older versions of python having more than one type of json lib. When the line from django.utils import simplejson is run, it goes to django/utils/simplejson/init.py which tries to use system versions of the json libs, and falls back on the one bundled with django. The old json package/module (python-json) doesn't have the right methods, so it raises an AttributeError. A simple fix is to test for JSONEncoder in the imported module, which is what the patch does.
