Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You wrote emit, and rush told you that word belongs to someone else. Here is how messaging is split. There is the what, and there is the how. The what is the message: the letter you want to send. The how is the delivery, and that belongs to the fedex, the engine's delivery service. Emit was one of the fedex's own tools, the hand that actually puts a letter into a mailbox. The ruling says only the fedex may call these. A program never reaches into another thread's memory. Instead, it says what it wants: message, the address of the thread, optionally two way, and the text. Rush then takes care of the delivery. So emit is retired for programs, and rush says so by name, instead of claiming it was not found. The fix is to replace emit with a message call, using the destination's gtrID. If you wrote your own function called emit, yours still wins. Say what you mean, and let the fedex do the carrying.
Text from the Rush engine's error catalogue.