Raise ImportError for old unsupported modules

theano/gpuarray/nerv.py

-from nose.plugins.skip import SkipTest
+# To prevent flake8 error.
+from __future__ import print_function, absolute_import, division
 
-raise SkipTest("You are importing theano.gpuarray.nerv. "
-               "This module was removed as it was based on nervanagpu that is now deprecated. "
-               "To still get this module, use Theano 0.9. "
-               "More info about nervanagpu here: https://github.com/NervanaSystems/nervanagpu "
-               "(viewed on 2017/07/05).")
+raise ImportError(
+    "You are importing theano.gpuarray.nerv. "
+    "This module was removed as it was based on nervanagpu that is now deprecated. "
+    "To still get this module, use Theano 0.9. "
+    "More info about nervanagpu here: https://github.com/NervanaSystems/nervanagpu "
+    "(viewed on 2017/07/05).")

theano/sandbox/cuda/__init__.py

-from nose.plugins.skip import SkipTest
-
-raise SkipTest(
+raise ImportError(
     "You are importing theano.sandbox.cuda. This is the old GPU back-end and "
     "is removed from Theano. Use Theano 0.9 to use it. Even better, "
     "transition to the new GPU back-end! See "