botserver: Exit with helpful output if botserverrc is invalid.

If the botserverrc file contains empty section headers, it
is very likely that the user forgot to edit the file. This
reminds them to do so.

zulip_botserver/zulip_botserver/server.py

@@ -2,7 +2,9 @@ import configparser
 import logging
 import json
 import os
+import sys
 
+from configparser import MissingSectionHeaderError
 from flask import Flask, request
 from importlib import import_module
 from typing import Any, Dict, Union, List, Optional
@@ -141,7 +143,12 @@ def handle_bot() -> Union[str, BadRequest, Unauthorized]:
 def main() -> None:
     options = parse_args()
     global bots_config
+    try:
         bots_config = read_config_file(options.config_file, options.bot_name)
+    except MissingSectionHeaderError:
+        sys.exit("Error: Your Botserver config file `{0}` contains an empty section header!\n"
+                 "You need to write the names of the bots you want to run in the "
+                 "section headers of `{0}`.".format(options.config_file))
     available_bots = list(bots_config.keys())
     bots_lib_modules = load_lib_modules(available_bots)
     third_party_bot_conf = parse_config_file(options.bot_config_file) if options.bot_config_file is not None else None