Fixed #13813 -- Comparison of DatabaseWrappers doesn't raise errors.

        self._thread_ident = thread.get_ident()

    def __eq__(self, other):

        if isinstance(other, BaseDatabaseWrapper):

            return self.alias == other.alias

        return NotImplemented

    def __ne__(self, other):

        return not self == other

from django.test import TestCase

from django.db.backends import BaseDatabaseWrapper

class DummyDatabaseWrapper(BaseDatabaseWrapper):

    pass

class DummyObject(object):

    alias = None

class DbBackendTests(TestCase):

    def test_compare_db_wrapper_with_another_object(self):

        wrapper = BaseDatabaseWrapper({})

        self.assertFalse(wrapper == 'not-a-db-wrapper')

    def test_compare_db_wrapper_with_another_object_with_alias(self):

        wrapper = BaseDatabaseWrapper({})

        obj = DummyObject()

        obj.alias = wrapper.alias = 'foobar'

        self.assertFalse(wrapper == obj)

    def test_negate_compare_db_wrapper_with_another_object(self):

        wrapper = BaseDatabaseWrapper({})

        self.assertTrue(wrapper != 'not-a-db-wrapper')

    def test_compare_db_wrappers(self):

        wrapper1 = DummyDatabaseWrapper({})

        wrapper2 = BaseDatabaseWrapper({})

        wrapper1.alias = wrapper2.alias = 'foo'

        self.assertTrue(wrapper1 == wrapper2)

        wrapper1.alias = 'bar'

        self.assertFalse(wrapper1 == wrapper2)