Patch `objects.get` so its DoesNotExist errors are more helpful

__init__.py

models.py

from django.conf import settings
from django.core.management import call_command
from django.db import models as m
from django.db.models import loading

from ..patch_objects_get import patch_objects_get

@patch_objects_get
class PatchObjectsGetDecoratorModel(m.Model):
    id = m.AutoField(primary_key=True)

class ModelTestBase(object):
    """ Adds 'tests.modules' INSTALLED_APPS and runs syncdb. """

    @classmethod
    def syncdb(cls):
        loading.cache.loaded = False
        call_command('syncdb', verbosity=0)

    @classmethod
    def setup_class(cls):
        cls.old_installed_apps = settings.INSTALLED_APPS
        module = ".".join(__name__.split(".")[:-1])
        settings.INSTALLED_APPS = (module, )
        cls.syncdb()

    @classmethod
    def teardown_class(cls):
        settings.INSTALLED_APPS = cls.old_installed_apps
        cls.syncdb()

patch_objects_get.py

from functools import wraps

def patch_objects_get(cls):
    """ Patch 'cls.objects.get' so its DoesNotExist errors will be more
        helpful.
        
        Usage:

        >>> @patch_objects_get
        ... class MyModel(m.Model):
        ...     pass
        ...
        >>> class MyOtherModel(m.Model):
        ...     pass
        ...
        >>> patch_objects_get(MyOtherModel)
        >>> MyModel.objects.get(id=3141)
        Traceback (most recent call last):
        ...
        DoesNotExist: MyModel matching {"id": 42} does not exist
        >>> """
    old_get = cls.objects.get

    @wraps(cls.objects.get)
    def get_wrapper(*args, **kwargs):
        try:
            return old_get(*args, **kwargs)
        except cls.DoesNotExist, e:
            e.args = ("%s matching %r does not exist"
                      %(cls.__name__, kwargs), )
            raise e

    cls.objects.get = get_wrapper
    return cls

test_patch_objects_get.py

from nose.tools import assert_equal

from ..patch_objects_get import patch_objects_get
from . import models as m

class TestManagers(m.ModelTestBase):

    def test_patch_objects_get(self):
        try:
            m.PatchObjectsGetDecoratorModel.objects.get(id=3141)
        except m.PatchObjectsGetDecoratorModel.DoesNotExist, e:
            assert "PatchObjectsGetDecoratorModel" in str(e)
            assert "3141" in str(e)
        else:
            raise AssertionError("expected error not raised")