Refs #31233 -- Changed DatabaseWrapper._nodb_connection to _nodb_cursor().

It is now a method instead of a property and returns a context manager
that yields a cursor on entry and closes the cursor and connection upon
exit.

tests/backends/postgresql/tests.py

@@ -4,24 +4,32 @@ from unittest import mock
 
 from django.core.exceptions import ImproperlyConfigured
 from django.db import DatabaseError, connection, connections
+from django.db.backends.base.base import BaseDatabaseWrapper
 from django.test import TestCase, override_settings
 
 
 @unittest.skipUnless(connection.vendor == 'postgresql', 'PostgreSQL tests')
 class Tests(TestCase):
+    databases = {'default', 'other'}
 
-    def test_nodb_connection(self):
+    def test_nodb_cursor(self):
         """
-        The _nodb_connection property fallbacks to the default connection
-        database when access to the 'postgres' database is not granted.
+        The _nodb_cursor() fallbacks to the default connection database when
+        access to the 'postgres' database is not granted.
         """
+        orig_connect = BaseDatabaseWrapper.connect
+
         def mocked_connect(self):
             if self.settings_dict['NAME'] is None:
                 raise DatabaseError()
-            return ''
+            return orig_connect(self)
 
-        nodb_conn = connection._nodb_connection
-        self.assertIsNone(nodb_conn.settings_dict['NAME'])
+        with connection._nodb_cursor() as cursor:
+            self.assertIs(cursor.closed, False)
+            self.assertIsNotNone(cursor.db.connection)
+            self.assertIsNone(cursor.db.settings_dict['NAME'])
+        self.assertIs(cursor.closed, True)
+        self.assertIsNone(cursor.db.connection)
 
         # Now assume the 'postgres' db isn't available
         msg = (
@@ -39,9 +47,13 @@ class Tests(TestCase):
                     'settings_dict',
                     {**connection.settings_dict, 'NAME': 'postgres'},
                 ):
-                    nodb_conn = connection._nodb_connection
-        self.assertIsNotNone(nodb_conn.settings_dict['NAME'])
-        self.assertEqual(nodb_conn.settings_dict['NAME'], connections['other'].settings_dict['NAME'])
+                    with connection._nodb_cursor() as cursor:
+                        self.assertIs(cursor.closed, False)
+                        self.assertIsNotNone(cursor.db.connection)
+        self.assertIs(cursor.closed, True)
+        self.assertIsNone(cursor.db.connection)
+        self.assertIsNotNone(cursor.db.settings_dict['NAME'])
+        self.assertEqual(cursor.db.settings_dict['NAME'], connections['other'].settings_dict['NAME'])
 
     def test_database_name_too_long(self):
         from django.db.backends.postgresql.base import DatabaseWrapper