Fix file name.

Author: lohedges

src/BioSimSpace/FreeEnergy/_relative.py

@@ -915,17 +915,17 @@ def _somd_extract(simfile, T=None, estimator="MBAR"):
 
         if not found_lambda:
             raise ValueError(
-                f"The lambda window was not detected in the SOMD output file: {file}"
+                f"The lambda window was not detected in the SOMD output file: {simfile}"
             )
 
         if not found_array:
             raise ValueError(
-                f"The lambda array was not detected in the SOMD output file: {file}"
+                f"The lambda array was not detected in the SOMD output file: {simfile}"
             )
 
         if not found_time:
             raise ValueError(
-                f"The simulation time was not detected in the SOMD output file: {file}"
+                f"The simulation time was not detected in the SOMD output file: {simfile}"
             )
 
         # TODO: get header from the file instead of like this.