Reciprocal space

The error raising on py3k is 
if I add raise ImportError after except like following 
        raise ImportError(" Failed to import ctrans - c routines for fast data anlysis ")
then it raise that error and Travis failed

However, if I don't raise an error and pass it ( that means after except : pass)
Then Travis tests passed without an error ( It can't be if the ctrans is not imported in the beginning??) I think may be the compatible issue, otherwise how can they (Travis tests) works without errors?