FIX: update error_file outputs to f string

Co-authored-by: Mathias Goncalves <[email protected]>

Author: mnoergaard

nipype/interfaces/freesurfer/model.py

@@ -519,7 +519,7 @@ def _list_outputs(self):
         outputs["dof_file"] = os.path.join(glmdir, "dof.dat")
         # Assign the conditional outputs
         if self.inputs.save_residual:
-            outputs["error_file"] = os.path.join(glmdir, "eres.{ext}")
+            outputs["error_file"] = os.path.join(glmdir, f"eres.{ext}")
         if self.inputs.save_estimate:
             outputs["estimate_file"] = os.path.join(glmdir, "yhat.{ext}")
         if any((self.inputs.mrtm1, self.inputs.mrtm2, self.inputs.logan)):