Fix incorrect requirement of FUGUE input

Author: oesteban

nipype/interfaces/fsl/preprocess.py

@@ -678,17 +678,17 @@ def _list_outputs(self):
                                                       '_variance.ext', cwd=cwd)
             outputs['std_img'] = self._gen_fname(outputs['out_file'] +
                                                  '_sigma.ext', cwd=cwd)
-                                                  
+
         # The mean image created if -stats option is specified ('meanvol')
-        # is missing the top and bottom slices. Therefore we only expose the 
-        # mean image created by -meanvol option ('mean_reg') which isn't 
+        # is missing the top and bottom slices. Therefore we only expose the
+        # mean image created by -meanvol option ('mean_reg') which isn't
         # corrupted.
         # Note that the same problem holds for the std and variance image.
-                                                  
+
         if isdefined(self.inputs.mean_vol) and self.inputs.mean_vol:
             outputs['mean_img'] = self._gen_fname(outputs['out_file'] +
                                                   '_mean_reg.ext', cwd=cwd)
-                                                  
+
         if isdefined(self.inputs.save_mats) and self.inputs.save_mats:
             _, filename = os.path.split(outputs['out_file'])
             matpathname = os.path.join(cwd, filename + '.mat')
@@ -1223,7 +1223,7 @@ class FUGUEInputSpec(FSLCommandInputSpec):
                                      requires=['fmap_out_file'],
                                      desc='saves the unmasked fieldmap when using --savefmap')
     save_unmasked_shift = traits.Bool(argstr='--unmaskshift',
-                                      requires=['shift_out_file'],
+                                      requires=['save_shift'],
                                       desc='saves the unmasked shiftmap when using --saveshift')
     nokspace = traits.Bool(
         argstr='--nokspace', desc='do not use k-space forward warping')