Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You told rush a holder lives in SQL, but you never said which SQL program to talk to. Here is the situation. Where sql is an umbrella: it can mean sqlite three, or another simple SQL tool. Rush does not choose one for you, and it does not bring one along. The project must name the binary, in the manifest dot rush file, with a line like sql equals, and the program's name. Without it, rush has nothing to run. It could have kept your data in memory, or in sulfur, or on disk, and let you believe it was in a database, but that would be a lie about where your data rests, and rush does not tell lies about data. So it refuses, naming the holder. Picture a script that declares a holder with where sql, and a manifest that never mentions sql. The second slot of the message gives the fix. Add the sql line to the manifest, naming the binary you want, run again, and the holder will rest in a real SQL database, exactly as declared.
Text from the Rush engine's error catalogue.