Handle all exceptions

If we get back an error that wasn't an APIError, it was causing the
thread to hang. This catch all, while I appreciate feels risky to
have a catch all, is better than not catching and silently failing,
with a never ending thread.

If something worse than an APIError has gone wrong, we want to stop
the incredible journey of what we're doing.

Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>

tests/integration/service_test.py

@@ -672,6 +672,25 @@ class ServiceTest(DockerClientTestCase):
         self.assertTrue(service.containers()[0].is_running)
         self.assertIn("ERROR: for 2  Boom", mock_stdout.getvalue())
 
+    @patch('sys.stdout', new_callable=StringIO)
+    def test_scale_with_api_returns_unexpected_exception(self, mock_stdout):
+        """
+        Test that when scaling if the API returns an error, that is not of type
+        APIError, that error is re-raised.
+        """
+        service = self.create_service('web')
+        next_number = service._next_container_number()
+        service.create_container(number=next_number, quiet=True)
+
+        with patch(
+            'compose.container.Container.create',
+                side_effect=ValueError("BOOM")):
+            with self.assertRaises(ValueError):
+                service.scale(3)
+
+        self.assertEqual(len(service.containers()), 1)
+        self.assertTrue(service.containers()[0].is_running)
+
     @patch('compose.service.log')
     def test_scale_with_desired_number_already_achieved(self, mock_log):
         """