Fixed Flake8 errors and error in copying stack trace.

theano/gof/opt.py

@@ -3019,8 +3019,6 @@ def check_stack_trace(f_or_fgraph, ops_to_check='last', bug_print='raise'):
             if (not hasattr(output.tag, 'trace') or not output.tag.trace):
                 print ('Failed on node')
                 print (node)
-                #print(node.outputs[0].tag.trace)
-                #print(node.tag.trace)
                 return False
 
     return True

theano/tensor/opt.py

@@ -4598,7 +4598,6 @@ def local_fill_cut(node):
     # from the removed fill op, it must come from the elemntwise op.
     copy_stack_trace(node.outputs, rval)
 
-
     if isinstance(rval, gof.Variable):
         return rval.owner.outputs
     else:
@@ -5158,6 +5157,7 @@ def local_sum_prod_mul_by_scalar(node):
                 new_op_input_nb_elements = new_op_input.size
                 new_op_output = node.op(new_op_input)
 
+            if not len(non_scalars) == 0:
                 # Copy over stacktrace from previous output to new mul op,
                 # for same reason as above.
                 copy_stack_trace(node.outputs, new_op_output)
@@ -5186,7 +5186,7 @@ def local_sum_prod_mul_by_scalar(node):
                 ret = T.mul(*mul_inputs)
                 # Copy over stacktrace from previous output to new mul op,
                 # for same reason as above.
-                copy_stack_trace(node.outputs, [ret]+mul_inputs)
+                copy_stack_trace(node.outputs, [ret] + mul_inputs)
 
                 return [ret]