patched doctest due to #1341 (comment)

Author: oesteban

nipype/interfaces/fsl/utils.py

@@ -184,7 +184,7 @@ class Smooth(FSLCommand):
     >>> sm.cmdline #doctest: +ELLIPSIS
     Traceback (most recent call last):
      ...
-    ValueError: Smooth requires a value for one of the inputs 'sigma'. ...
+    ValueError: Smooth requires a value for one of the inputs ...
 
     """