Wait-for-db periodically fails on startup

app/core/management/commands/wait_for_db.py

@@ -10,10 +10,12 @@ class Command(BaseCommand):
 
     def handle(self, *args, **options):
         self.stdout.write('Waiting for database...')
-        db_conn = None
-        while not db_conn:
+        cursor = None
+        while not cursor:
             try:
                 db_conn = connections['default']
+                self.stdout.write('Obtain cursor and verify database...')
+                cursor = db_conn.cursor()
             except OperationalError:
                 self.stdout.write('Database unavailable, waiting 1 second...')
                 time.sleep(1)

app/core/tests/test_commands.py

@@ -1,4 +1,4 @@
-from unittest.mock import patch
+from unittest.mock import patch, MagicMock
 
 from django.core.management import call_command
 from django.db.utils import OperationalError
@@ -9,15 +9,16 @@ class CommandTests(TestCase):
 
     def test_wait_for_db_ready(self):
         """Test waiting for db when db is available"""
-        with patch('django.db.utils.ConnectionHandler.__getitem__') as gi:
-            gi.return_value = True
+        conn = MagicMock(return_value=None)
+        with patch('django.db.utils.ConnectionHandler.__getitem__', return_value=conn):
             call_command('wait_for_db')
-            self.assertEqual(gi.call_count, 1)
+            conn.cursor.assert_called_once()
 
-    @patch('time.sleep', return_value=True)
+    @patch('time.sleep', return_value=None)
     def test_wait_for_db(self, ts):
         """Test waiting for db"""
-        with patch('django.db.utils.ConnectionHandler.__getitem__') as gi:
-            gi.side_effect = [OperationalError] * 5 + [True]
+        conn = MagicMock(return_value=None)
+        with patch('django.db.utils.ConnectionHandler.__getitem__', return_value=conn):
+            conn.cursor.side_effect = [OperationalError] * 5 + [True]
             call_command('wait_for_db')
-            self.assertEqual(gi.call_count, 6)
+            self.assertEqual(conn.cursor.call_count, 6)