Review fixes and correc check for var.owner

theano/compile/nanguardmode.py

@@ -282,8 +282,8 @@ class NanGuardMode(Mode):
                           " output of a node in this variable:", file=sio)
                     print(theano.printing.debugprint(nd, file='str'), file=sio)
                 else:
-                    print("NanGuardMode found an error in the"
-                          " input %d of this node.", file=sio)
+                    print("NanGuardMode found an error in an"
+                          " input of this node." , file=sio)
                     print('Node:', file=sio)
                     print(nd, file=sio)
                     print("The input variable that cause problem:", file=sio)
@@ -318,7 +318,7 @@ class NanGuardMode(Mode):
                 # If the input is the result of computation, then we
                 # don't need to check it. It is already done after the
                 # computation.
-                if not var.owner:
+                if var.owner is not None:
                     do_check_on(x[0], node, fn, True)
             fn()
             outputs = fn.outputs

theano/gof/link.py

@@ -306,7 +306,7 @@ def raise_with_op(node, thunk=None, exc_info=None, storage_map=None):
         exc_value = exc_type(str(exc_value) + detailed_err_msg +
                              '\n' + '\n'.join(hints))
     except TypeError:
-        print("WARNING: %s error do not allow us to add extra error message" %
+        print("WARNING: %s error does not allow us to add extra error message" %
               str(exc_type))
         # Some exception need extra parameter in inputs. So forget the
         # extra long error message in that case.

theano/sandbox/cuda/dnn.py

@@ -2389,7 +2389,6 @@ if True:
              (node.inputs[1].owner and
                  isinstance(node.inputs[1].owner.op, HostFromGpu)))):
             if not dnn_available():
-                # Softmax grad is broken in v3 rc1 for this case
                 return
             ins = []
             for n in node.inputs:

theano/sandbox/cuda/opt.py

@@ -797,7 +797,7 @@ def local_gpu_careduce(node):
                 replace = True
             # If this is a useless reduce, remove it as
             # local_cut_useless_reduce.  This is needed as the code
-            # bellow do not support when x.ndim == 0.
+            # below do not support when x.ndim == 0.
             if x.type == node.outputs[0].type:
                 return [x]
             elif (all([c != "output" and isinstance(c.op, GpuFromHost)