Looper: missing argument error
You are using the argument values incorrectly. Argument values are sample attributes, not full character paths. Hence, "IU" is a sample attribute, "gencode_mouse_m13" is a sample attribute, so why would you think "/scratch..." would be treated any differently?

The pipeline interface maps sample attributes to command-line arguments. It is modulated by sample (different values per sample). What you're trying to do is pass a constant string to an argument.

For this, there is a pipeline_args section of your project config. Please read the docs on project config.