Raise KnownFailureTest instead of printing to stderr.

theano/compile/tests/test_function_module.py

@@ -9,8 +9,9 @@ from theano.compile import function
 from theano import tensor
 from theano import tensor as T
 import random, theano
-import numpy as N
 
+import numpy as N
+from numpy.testing.noseclasses import KnownFailureTest
 
 PatternOptimizer = lambda p1, p2, ign=True: gof.OpKeyOptimizer(gof.PatternSub(p1, p2), ignore_newtrees=ign)
 
@@ -33,7 +34,7 @@ class T_function(unittest.TestCase):
         fn = function([], None) #ok
         rval = fn()
         if rval == []:
-            print >> sys.stderr, 'WARNING: ticket #254'
+            raise KnownFailureTest('See #254: Using None as function output leads to [] return value')
         else:
             assert rval is None