fix "Got unknown tag" warning
fix "Got unknown tag" warning

- Remove extra "\n"
- Use warning(fmt, args) instead of warning(fmt % (args))

Signed-off-by: Eduardo Habkost <50373d7c08ceadf576dd7dca718012445b677ce6@raisama.net>

dustin/twitty-twister,praekelt/twitty-twister