mnist example: serializing the pipeline

[florinb]

Hi, I am running the mnist example on a free databricks account and I cannot get a valid bundle file for the pipeline. The code runs without any errors but the zip file is empty. Switching to a directory based serialization does seem to produce a valid export of the pipeline. The Databricks cluster is Spark 2.2.0, scala 2.11. What am I doing wrong? Thanks

Attached is the bundle zip file I get.
mnist-spark-pipeline-01.zip