Fixed #14711 -- Corrected the calculation for the previous month in generic...

        Get the previous valid month.

        """

        first_day, last_day = _month_bounds(date)

        prev = (first_day - datetime.timedelta(days=1)).replace(day=1)

        prev = (first_day - datetime.timedelta(days=1))

        return _get_next_prev_month(self, prev, is_previous=True, use_first_day=True)

    This is a bit complicated since it handles both next and previous months

    and days (for MonthArchiveView and DayArchiveView); hence the coupling to generic_view.

    However in essance the logic comes down to:

    However in essence the logic comes down to:

        * If allow_empty and allow_future are both true, this is easy: just

          return the naive result (just the next/previous day or month,

    # whose date_field is at least (greater than/less than) the given

    # naive result

    else:

        # Construct a lookup and an ordering depending on weather we're doing

        # Construct a lookup and an ordering depending on whether we're doing

        # a previous date or a next date lookup.

        if is_previous:

            lookup = {'%s__lte' % date_field: naive_result}

        result = result.date()

    # For month views, we always want to have a date that's the first of the

    # month for consistancy's sake.

    # month for consistency's sake.

    if result and use_first_day:

        result = result.replace(day=1)

        res = self.client.get('/dates/books/2007/no_month/')

        self.assertEqual(res.status_code, 404)

    def test_previous_month_without_content(self):

        "Content can exist on any day of the previous month. Refs #14711"

        self.pubdate_list = [

            datetime.date(2010, month, day)

            for month,day in ((9,1), (10,2), (11,3))

        ]

        for pubdate in self.pubdate_list:

            name = str(pubdate)

            Book.objects.create(name=name, slug=name, pages=100, pubdate=pubdate)

        res = self.client.get('/dates/books/2010/nov/allow_empty/')

        self.assertEqual(res.status_code, 200)

        self.assertEqual(res.context['previous_month'], datetime.date(2010,10,1))

        # The following test demonstrates the bug

        res = self.client.get('/dates/books/2010/nov/')

        self.assertEqual(res.status_code, 200)

        self.assertEqual(res.context['previous_month'], datetime.date(2010,10,1))

        # The bug does not occur here because a Book with pubdate of Sep 1 exists

        res = self.client.get('/dates/books/2010/oct/')

        self.assertEqual(res.status_code, 200)

        self.assertEqual(res.context['previous_month'], datetime.date(2010,9,1))

class WeekArchiveViewTests(TestCase):

    fixtures = ['generic-views-test-data.json']

    urls = 'regressiontests.generic_views.urls'

    def test_invalid_url(self):

        self.assertRaises(AttributeError, self.client.get, "/dates/books/2008/oct/01/nopk/")