refactoring test

Author: dantownsend

tests/apps/migrations/commands/test_forwards_backwards.py

@@ -120,10 +120,17 @@ def test_backwards_unknown_migration(self, print_: MagicMock):
                 )
             )
 
-        self.assertTrue(
-            print_.mock_calls[0]
-            .args[0]
-            .startswith("Unrecognized migration name - must be one of ")
+        self.assertEqual(
+            len(
+                [
+                    i
+                    for i in print_.mock_calls
+                    if i.args[0].startswith(
+                        "Unrecognized migration name - must be one of "
+                    )
+                ]
+            ),
+            1,
         )
 
     @patch("piccolo.apps.migrations.commands.backwards.print")