Enhance test assertions with detailed error messages

tests/test_main.py

@@ -5,9 +5,11 @@ from discord_reminder_bot import main
 
 def test_if_send_to_discord_is_in_main() -> None:
     """send_to_discords needs to be in main for this program to work."""
-    assert hasattr(main, "send_to_discord")
+    assert_msg: str = f"send_to_discord is not in main. Current functions in main: {dir(main)}"
+    assert hasattr(main, "send_to_discord"), assert_msg
 
 
 def test_if_send_to_user_is_in_main() -> None:
     """send_to_user needs to be in main for this program to work."""
-    assert hasattr(main, "send_to_user")
+    assert_msg: str = f"send_to_user is not in main. Current functions in main: {dir(main)}"
+    assert hasattr(main, "send_to_user"), assert_msg