Fixed small mistake.

theano/sandbox/linalg/kron.py

 from theano import tensor
 from theano.tensor.slinalg import kron
+import warnings
 
 warnings.warn(
         "theano modules are deprecated and will be removed in release 0.7",

theano/tensor/var.py

@@ -535,7 +535,7 @@ class _tensor_py_operators:
         return theano.tensor.basic.round(self, mode)
 
     def trace(self):
-        return theano.sandbox.linalg.trace(self)
+        return theano.sandbox.linalg.ops.trace(self)
 
     # TO TRUMP NUMPY OPERATORS
     __array_priority__ = 1000