Fix another import error

theano/sandbox/gpuarray/opt.py

@@ -16,7 +16,7 @@ from theano.scan_module import scan_utils, scan_op, scan_opt
 
 from theano.tensor import as_tensor_variable
 from theano.tensor.nnet.conv import ConvOp
-from theano.tensor.nnet.abstract_conv2d import (BaseAbstractConv2d,
+from theano.tensor.nnet.abstract_conv import (BaseAbstractConv2d,
                                               AbstractConv2d,
                                               AbstractConv2d_gradWeights,
                                               AbstractConv2d_gradInputs)