noticed that this error also happens for 'out_grad_fsl'. Fixed it

Author: GalKepler

nipype/interfaces/mrtrix3/preprocess.py

@@ -192,7 +192,9 @@ class DWIBiasCorrectInputSpec(MRTrix3BaseInputSpec):
         mandatory=True,
         desc="input DWI image",
     )
-    in_mask = File(argstr="-mask %s", desc="input mask image for bias field estimation")
+    in_mask = File(
+        argstr="-mask %s", desc="input mask image for bias field estimation"
+    )
     use_ants = traits.Bool(
         argstr="ants",
         mandatory=True,
@@ -407,8 +409,10 @@ def _list_outputs(self):
         outputs = self.output_spec().get()
         outputs["out_file"] = op.abspath(self.inputs.out_file)
         if self.inputs.out_grad_mrtrix:
-            outputs["out_grad_mrtrix"] = op.abspath(self.inputs.out_grad_mrtrix)
-        if self.inputs.export_grad_fsl:
+            outputs["out_grad_mrtrix"] = op.abspath(
+                self.inputs.out_grad_mrtrix
+            )
+        if self.inputs.out_fsl_bvec:
             outputs["out_fsl_bvec"] = op.abspath(self.inputs.out_grad_fsl[0])
             outputs["out_fsl_bval"] = op.abspath(self.inputs.out_grad_fsl[1])
 
@@ -441,9 +445,15 @@ class ResponseSDInputSpec(MRTrix3BaseInputSpec):
         usedefault=True,
         desc="output WM response text file",
     )
-    gm_file = File(argstr="%s", position=-2, desc="output GM response text file")
-    csf_file = File(argstr="%s", position=-1, desc="output CSF response text file")
-    in_mask = File(exists=True, argstr="-mask %s", desc="provide initial mask image")
+    gm_file = File(
+        argstr="%s", position=-2, desc="output GM response text file"
+    )
+    csf_file = File(
+        argstr="%s", position=-1, desc="output CSF response text file"
+    )
+    in_mask = File(
+        exists=True, argstr="-mask %s", desc="provide initial mask image"
+    )
     max_sh = InputMultiObject(
         traits.Int,
         argstr="-lmax %s",