small fix from code review

doc/tutorial/examples.txt

@@ -476,7 +476,7 @@ work on the CPU and GPU. CURAND only work on the GPU.
 
         .. code-block:: python
 
-            from theano.sandbox.rng_mrg import MRG_RandomStreams
+            from theano.sandbox.rng_mrg import MRG_RandomStreams as RandomStreams
 
 .. _logistic_regression:
 

theano/sandbox/cuda/opt_util.py

@@ -74,7 +74,6 @@ def alpha_merge(cls, alpha_in, beta_in, nd):
                     return None
                 inputs = list(targ.inputs)
                 try:
-                    raise NotScalarConstantError()
                     c = get_scalar_constant_value(lr)
                     if c == 0:
                         inputs[alpha_in] = lr