Improve Python 3 compatibility in example notebooks

examples/notebooks/Frontend-Kernel Model.ipynb

@@ -153,9 +153,8 b''
      "collapsed": false,
      "input": [
       "# Python 3 compat\n",
-      "try:\n",
-      "    raw_input\n",
-      "except NameError:\n",
+      "import sys\n",
+      "if sys.version_info[0] >= 3:\n",
       "    raw_input = input"
      ],
      "language": "python",

examples/notebooks/Importing Notebooks.ipynb

@@ -157,7 +157,7 b''
       "                # transform the input to executable Python\n",
       "                code = self.shell.input_transformer_manager.transform_cell(cell.input)\n",
       "                # run the code in themodule\n",
-      "                exec code in mod.__dict__\n",
+      "                exec(code, mod.__dict__)\n",
       "        finally:\n",
       "            self.shell.user_ns = save_user_ns\n",
       "        return mod\n"