502 Bad Gateway when running bring your own model

[Notebook](https://github.com/aws/amazon-sagemaker-examples/blob/default/%20%20%20%20%20deploy_and_monitor/sm-xgboost_bring_your_own_model/sm-xgboost_bring_your_own_model.ipynb)

**Describe the bug**
502 Bad Gateway response from endpoint.

**To reproduce**
Run each cell in order to load data, train model and persist to endpoint. Running in East Us 2 region.

**Logs**

Open deploy_and_monitor/sm-xgboost_bring_your_own_model/sm-xgboost_bring_your_own_model.ipynb and review the attached 502 log. Run the notebook cells in order in the East US 2 region, including training and persisting the model to an endpoint. Done means the endpoint no longer returns a 502 Bad Gateway response.

Written by the indexing model from the issue text.