Add non-abstract poll_exception method to MyRunner in custom botorch model tutorial (#2087)

Summary:
## Motivation

[Ax https://github.com/pytorch/botorch/issues/1958](https://github.com/facebook/Ax/pull/1958) broke the custom botorch model tutorial by adding an abstract method to the `Runner` class; the tutorial contained a `Runner` subclass that did not override this method. I fixed this by adding a method that returns a `NotImplementedError`.

Pull Request resolved: #2087

Test Plan: Ran tutorial locally: `python scripts/run_tutorials.py -p "$(pwd)" -s -n custom_botorch_model_in_ax.ipynb`

Reviewed By: saitcakmak

Differential Revision: D51046160

Pulled By: esantorella

fbshipit-source-id: dd3b86f379f44be51fda01cbc412559a1e84b475

Author: esantorella

tutorials/custom_botorch_model_in_ax.ipynb

@@ -91,7 +91,6 @@
         "from typing import Optional\n",
         "\n",
         "from botorch.models.gpytorch import GPyTorchModel\n",
-        "from botorch.utils.datasets import SupervisedDataset\n",
         "from gpytorch.distributions import MultivariateNormal\n",
         "from gpytorch.kernels import RBFKernel, ScaleKernel\n",
         "from gpytorch.likelihoods import GaussianLikelihood\n",
@@ -1140,6 +1139,15 @@
         "        trial_metadata = {\"name\": str(trial.index)}\n",
         "        return trial_metadata\n",
         "\n",
+        "    def poll_exception(self, trial) -> str:\n",
+        "        \"\"\"\n",
+        "        Returns the exception from a trial if present. In this case, we do not\n",
+        "        expect that trials will have attached exceptions.\n",
+        "        \"\"\"\n",
+        "        raise NotImplementedError(\n",
+        "            f\"{self.__class__.__name__} does not implement a `poll_exception` method.\"\n",
+        "        )\n",
+        "\n",
         "\n",
         "exp = Experiment(\n",
         "    name=\"branin_experiment\",\n",