Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You declared a module, and then put nothing inside it. The engine refuses that, at parse. A module is a scope: a place that holds values and functions. If the header says module and there is no indented body underneath, then the scope holds nothing. And a scope that holds nothing has no reason to exist. It is like putting up a sign for a shop and never opening the door. Why does it matter? Because a module name is a promise to the reader that something useful lives there. An empty module breaks the promise and adds noise to the structure of the project. It also tends to be a leftover, from a half finished edit or a file you meant to come back to. The message names the empty module. The fix is one of two things. Put something in it, a value or a function. Or delete the header. Either way, the structure of your project will say only what is true.
Text from the Rush engine's error catalogue.