modify download demo for python3

tensorflow2fluid/vgg_translate_tutorial.ipynb

@@ -16,10 +16,14 @@
    "metadata": {},
    "outputs": [
     {
-     "name": "stderr",
-     "output_type": "stream",
-     "text": [
-      "Download percentage 100.00%"
+     "ename": "AttributeError",
+     "evalue": "module 'urllib' has no attribute 'urlretrieve'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-1-20ecf9db141f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      8\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[0murl\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m\"http://download.tensorflow.org/models/vgg_16_2016_08_28.tar.gz\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 10\u001b[0;31m \u001b[0mfetch\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0murllib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0murlretrieve\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0murl\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m\"./vgg_16.tar.gz\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mschedule\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m: module 'urllib' has no attribute 'urlretrieve'"
      ]
     }
    ],
@@ -341,21 +345,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python [conda env:GPU-Paddle]",
+   "display_name": "tensorflow",
    "language": "python",
-   "name": "conda-env-GPU-Paddle-py"
+   "name": "tensorflow"
   },
   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
    },
    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
-   "version": "2.7.15"
+   "pygments_lexer": "ipython3",
+   "version": "3.5.6"
   },
   "varInspector": {
    "cols": {