Merge pull request #2375 from djarecka/RealignInputSpec_update

trait changes in RealignInputSpec (fixes #2120)

Author: mgxd

nipype/interfaces/spm/preprocess.py

@@ -125,8 +125,7 @@ def _list_outputs(self):
 
 class RealignInputSpec(SPMCommandInputSpec):
     in_files = InputMultiPath(
-        traits.Either(
-            traits.List(ImageFileSPM(exists=True)), ImageFileSPM(exists=True)),
+        ImageFileSPM(exists=True),
         field='data',
         mandatory=True,
         copyfile=True,