fix by_list test

tests/test_client.py

@@ -523,6 +523,16 @@ class ClientTests(unittest.TestCase):
                                obj.ticket_get_by_list,
                                1)
 
+    def test_ticket_get_by_list_fail_string_provided(self):
+        """Tests ticket_get_by_list fail int was provided"""
+        obj = Client(baseurl="http://fqdn", webservicename="GenericTicketConnectorREST")
+        obj.session_id_store.value = "some_session_id"
+
+        self.assertRaisesRegex(ArgumentInvalidError,
+                               "Please provide list of IDs!",
+                               obj.ticket_get_by_list,
+                               "4711")
+
     @mock.patch('pyotrs.Client._send_request')
     @mock.patch('pyotrs.Client._parse_and_validate_response', autospec=True)
     def test_ticket_get_by_list_ok(self, mock_parse_validate, mock_send_req):