Revert imports to fix Python 3.6 circular import error

theano/tensor/opt_uncanonicalize.py

@@ -33,12 +33,12 @@ supposed to be canonical.
 
 import logging
 
-import theano.tensor.basic as tt
-import theano.scalar.basic as scal
+from theano.tensor.elemwise import CAReduce
+from theano.tensor import basic as tt
+from theano import scalar as scal
+from theano.tensor import DimShuffle, Subtensor
 
 from theano.gof.opt import copy_stack_trace, local_optimizer
-from theano.tensor.subtensor import Subtensor
-from theano.tensor.elemwise import CAReduce, DimShuffle
 from theano.tensor.opt import register_uncanonicalize
 
 _logger = logging.getLogger("theano.tensor.opt")