configuration: improved config file format

tests/test_chat.py

@@ -481,3 +481,8 @@ class TestChatDB(unittest.TestCase):
         chat_db.update_messages([message], write=True)
         chat_db.read_db()
         self.assertEqual(chat_db.messages[0].answer, Answer("New answer"))
+        # test without file_path -> expect error
+        message1 = Message(question=Question("Question 1"),
+                           answer=Answer("Answer 1"))
+        with self.assertRaises(ChatError):
+            chat_db.update_messages([message1])