zulip_bots and zulip_botserver: Remove unused imports.

zulip_botserver/setup.py

@@ -3,7 +3,6 @@
 
 from __future__ import print_function
 
-import os
 import sys
 if False:
     from typing import Any, Dict, Optional

zulip_botserver/tests/server_test_lib.py

@@ -1,8 +1,7 @@
 import json
 
-from typing import Any, List, Dict, Optional, Union
+from typing import Any, List, Dict, Optional
 from unittest import TestCase
-from werkzeug.exceptions import BadRequest
 from zulip_botserver import server