Fix for FUGUE interface

Run autopep8 on preprocess.py. autopep8 would not correct some error
though (those that might change code's behaviour, like breaklines)
Note: I had a broken fork of nipype, disregard previous reference from
commit.

Close nipy/nipype#642.
Minor detail fixed

Regards nipy/nipype#644
Merge pull request #644 from oesteban/bug/FixFugueInterface

Fix for FUGUE interface