PEP8 and minor rephrasing

theano/gof/op.py

@@ -468,17 +468,17 @@ class PureOp(object):
 
 
         returns: a list of n elements
-                    rval[i] should be Rop(f = f_i(inputs),
-                                          wrt = inputs,
-                                          eval_points = eval_points)
+                    rval[i] should be Rop(f=f_i(inputs),
+                                          wrt=inputs,
+                                          eval_points=eval_points)
 
         """
-
-        raise NotImplementedError(str(self)+' of type '+str(self.__class__.__name__)
-                +" does not "
+        raise NotImplementedError(
+                "%s of class %s does not "
                 "implement R_op. If this is a theano op, write to the "
                 "theano-dev mailing list for assistance. If it is your "
-                "own op, implement the R_op method.")
+                "own op, implement the R_op method." %
+                (self, self.__class__.__name__))
 
 
     def perform(self, node, inputs, output_storage):

theano/tensor/tensor_grad.py

@@ -94,8 +94,8 @@ def Rop(f, wrt, eval_points):
 
     assert len(wrt) == len(eval_points)
 
-    #check that each element of wrt corresponds to an element
-    #of eval_points with the same dimensionality
+    # Check that each element of wrt corresponds to an element
+    # of eval_points with the same dimensionality.
     for pack in enumerate(zip(wrt, eval_points)):
         i = pack[0]
         wrt_elem, eval_point = pack[1]