Fixed #15786 -- Added a regression test for o2o excludes using F().

    def __str__(self):

        return "one2one " + self.new_name

class CategoryRelationship(models.Model):

    first = models.ForeignKey(SimpleCategory, related_name='first_rel')

    second = models.ForeignKey(SimpleCategory, related_name='second_rel')

class NullableName(models.Model):

    name = models.CharField(max_length=20, null=True)

import datetime

from operator import attrgetter

import pickle

import sys

import unittest

from django.conf import settings

    OneToOneCategory, NullableName, ProxyCategory, SingleObject, RelatedObject,

    ModelA, ModelB, ModelC, ModelD, Responsibility, Job, JobResponsibilities,

    BaseA, FK1, Identifier, Program, Channel, Page, Paragraph, Chapter, Book,

    MyObject, Order, OrderItem, SharedConnection, Task, Staff, StaffUser)

    MyObject, Order, OrderItem, SharedConnection, Task, Staff, StaffUser,

    CategoryRelationship)

class BaseQuerysetTest(TestCase):

    def assertValueQuerysetEqual(self, qs, values):

            Order.objects.exclude(~Q(items__status=1)).distinct(),

            ['<Order: 1>'])

class Exclude15786(TestCase):

    """Regression test for #15786"""

    def test_ticket15786(self):

        c1 = SimpleCategory.objects.create(name='c1')

        c2 = SimpleCategory.objects.create(name='c2')

        o2o1 = OneToOneCategory.objects.create(category=c1)

        o2o2 = OneToOneCategory.objects.create(category=c2)

        rel = CategoryRelationship.objects.create(first=c1, second=c2)

        self.assertEqual(

            CategoryRelationship.objects.exclude(

                first__onetoonecategory=F('second__onetoonecategory')

            ).get(), rel

        )

class NullInExcludeTest(TestCase):

    def setUp(self):

        NullableName.objects.create(name='i1')