Minor changes.

theano/sandbox/multinomial.py

@@ -22,24 +22,24 @@ class Multinomial(Op):
         self.__dict__.update(dct)
         try:
             self.odtype
-        except:
+        except AttributeError:
             self.odtype='auto'
     def make_node(self, pvals, unis):
         pvals = T.as_tensor_variable(pvals)
         unis = T.as_tensor_variable(unis)
         if pvals.ndim != 2:
-            raise NotImplementedError('pvals ndim', pvals.ndim)
+            raise NotImplementedError('pvals ndim should be 2', pvals.ndim)
         if unis.ndim != 1:
-            raise NotImplementedError('unis ndim', unis.ndim)
+            raise NotImplementedError('unis ndim should be 1', unis.ndim)
         if self.odtype=='auto':
             odtype = pvals.dtype
         else:
             odtype = self.odtype
         return Apply(self, [pvals, unis], [T.matrix(dtype=odtype)])
 
-    def grad(self, ins, outs):
+    def grad(self, ins, outgrads):
         pvals, unis = ins
-        (gz,) = outs
+        (gz,) = outgrads
         return [None, None]
 
     def c_code_cache_version(self):
@@ -134,7 +134,7 @@ class GpuMultinomial(Multinomial):
         else:
             odtype = self.odtype
         if odtype != pvals.dtype:
-            raise NotImplementedError()
+            raise NotImplementedError('GpuMultinomial works only if self.odtype == pvals.dtype', odtype, pvals.dtype)
         return Apply(self, [pvals, unis], [pvals.type()])
 
     def c_code_cache_version(self):