Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
Here is a strange one: the engine tried to refuse something, and the refusal itself was not on file. Every refusal in rush has an id and a home in the catalogue, errors.feml. That catalogue is the promise that every no the engine says can be explained to you. This time, the engine reached for an id that is not in the catalogue. Either nobody ever declared it, or it was declared and then unplugged. So the engine wanted to say no, but had no words for it. Think of a referee who blows the whistle and then realizes the rulebook has no page for the foul. That is not your fault. Your script did not cause this; the engine did. Under a proper design this situation should be impossible to construct, which is exactly why it is reported loudly instead of being hidden. What can you do? Look at the code in the message: that is the missing id. If you are building the engine, add the refusal to errors.feml, or find out why the declaration vanished. If you are a script author, report it, with the code, so the catalogue can be completed. One missing page, and the whole rulebook gets stronger.
Text from the Rush engine's error catalogue.