Issue warning to user for legacy options

Author: berland

src/runrms/_forward_model.py

@@ -3,6 +3,7 @@
     ForwardModelStepJSON,
     ForwardModelStepPlugin,
     ForwardModelStepValidationError,
+    ForwardModelStepWarning,
     plugin,
 )
 
@@ -55,6 +56,17 @@ def validate_pre_experiment(self, fm_step_json: ForwardModelStepJSON) -> None:
         if not ok:
             raise ForwardModelStepValidationError(f"FMRMSConfig: {err}")
 
+        if "<RMS_PYTHONPATH>" in self.private_args:
+            ForwardModelStepWarning.warn(
+                "Remove unused option <RMS_PYTHONPATH> from your RMS step "
+                "configuration. It has no effect."
+            )
+        if "<RMS_PATH_PREFIX>" in self.private_args:
+            ForwardModelStepWarning.warn(
+                "Remove unused option <RMS_PATH_PREFIX> from your RMS step "
+                "configuration. It has no effect."
+            )
+
     @staticmethod
     def documentation() -> ForwardModelStepDocumentation | None:
         return ForwardModelStepDocumentation(