Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You asked rush to run a script file, and the engine could not read it. Think about what the alternative would have been. If the engine had treated the unreadable file as empty, it would have parsed nothing, run nothing, and reported success. A successful run of a program nobody wrote. That would be a lie, so the engine refuses by name instead. The message gives you the file path and the reason. There are three common reasons. The file may not exist, so check the spelling and the folder. The file may exist but be unreadable, so check the permissions. Or it may be larger than this engine is willing to hold, so check the size. For example, running a script with a mistyped path will land you right here. The fix is almost always one of those three. Open a terminal, list the file, make sure you can read it, and run again. The point of this refusal is simple: if rush cannot read what you asked it to run, it tells you, instead of pretending the job was done.
Text from the Rush engine's error catalogue.