better DISCORD_TOKEN error

starbot/starbot/__main__.py

@@ -13,7 +13,15 @@ from .db import AbstractDbFactory
 
 async def _main():
     token = os.getenv("DISCORD_TOKEN")
-    assert token is not None
+    if token is None:
+        print(
+            """\
+DISCORD_TOKEN environment variable is not set
+edit .secrets/starbot.env with the following content (substitute <token here> with the token):
+DISCORD_TOKEN = <token here>\
+"""
+        )
+        exit(1)
     dbfm = os.getenv("DBF_MODULE")
     assert dbfm is not None
     DBF: AbstractDbFactory = importlib.import_module(dbfm).DBF