Thanks for posting the challenge you are running into!
Are you using the dataflow runner, by chance? If so, then you can try hardcoding the exportNameSuffix parameter. Working with @mjoshi, author of the Dataflow runner, he isolated a condition where exportNameSuffix is not set, likely triggering the error you saw. Let me know if you have additional questions about the above.
Note The dataflow runner was written in Python 2.7. I expect the cluster you are using is also using 2.7. If you are not sure, please select About from the user menu in the top-right corner of your Xcalar Design window and tell us your cluster version.
If you are not using the dataflow runner, then please give me additional details about the steps you were executing when you ran into the error above.