add error handling for env vars; run pre-commit (#43)

src/karmabot/settings.py

@@ -1,23 +1,44 @@
+import logging
 import os
 import re
 from pathlib import Path
 
 from dotenv import load_dotenv
 from slackclient import SlackClient
 
+
+def _get_env_var(env_var: str):
+    env_var_value = os.environ.get(env_var)
+
+    # explicit check for None as None is returned by environ.get for non existing keys
+    if env_var_value is None:
+        raise KeyError(
+            f"{env_var} was not found. Please check your .karmabot file as well as the README.md."
+        )
+
+    if not env_var_value:
+        raise ValueError(
+            f"{env_var} was found but seems empty. Please check your .karmabot file as well as the README.md."
+        )
+
+    return env_var_value
+
+
 dotenv_path = Path(".").resolve() / ".karmabot"
 if dotenv_path.exists():
+    logging.info("Loading environmental variables from .karmabot.")
     load_dotenv(dotenv_path)
 
 # Environment variables
-KARMABOT_ID = os.environ.get("KARMABOT_SLACK_USER")
-SLACK_TOKEN = os.environ.get("KARMABOT_SLACK_TOKEN")
-SLACK_INVITE_TOKEN = os.environ.get("KARMABOT_SLACK_INVITE_USER_TOKEN")
-DATABASE_URL = os.environ.get("KARMABOT_DATABASE_URL")
+KARMABOT_ID = _get_env_var("KARMABOT_SLACK_USER")
+SLACK_TOKEN = _get_env_var("KARMABOT_SLACK_TOKEN")
+SLACK_INVITE_TOKEN = _get_env_var("KARMABOT_SLACK_INVITE_USER_TOKEN")
+DATABASE_URL = _get_env_var("KARMABOT_DATABASE_URL")
 
 # Slack
-GENERAL_CHANNEL = os.environ.get("KARMABOT_GENERAL_CHANNEL")
-ADMINS = os.environ.get("KARMABOT_ADMINS").split(",")  # type: ignore
+GENERAL_CHANNEL = _get_env_var("KARMABOT_GENERAL_CHANNEL")
+ADMINS = _get_env_var("KARMABOT_ADMINS")
+ADMINS = ADMINS.split(",")  # type: ignore
 SLACK_ID_FORMAT = re.compile(r"^<@[^>]+>$")
 SLACK_CLIENT = SlackClient(SLACK_TOKEN)