Portable Beam failed to run Python wordcount on Flink

Recently I tried to run portable python wordcount example following exactly what it says in the guide page [https://beam.apache.org/roadmap/portability/](https://beam.apache.org/roadmap/portability/,), but still no luck after several days trying.

*Here're my steps,*
1. ./gradlew :beam-sdks-python-container:docker (to build the sdk container, no error)
2. ./gradlew :beam-runners-flink_2.11-job-server:installShadowDist (to build jobservice jar, no error)
3. ./gradlew :beam-runners-flink_2.11-job-server:runShadow -PflinkMasterUrl=localhost:8081 (to run jobservice, no error)
4. ./gradlew :beam-sdks-python:portableWordCount -PjobEndpoint=localhost:8099 (to submit wordcount job, error as mentioned below)

*Have seen 2 errors, sometime, it says,*
> BeamIOError: src and dst files do not exist. src: /tmp/beam-temp-py-wordcount-direct-56d037a2ffa611e88f9208002721555c/020e033b-ec4f-495f-bfa4-e49b59ef9d36.py-wordcount-direct, dst: /tmp/py-wordcount-direct-00000-of-00001 with exceptions None [while running 'write/Write/WriteImpl/FinalizeWrite'] with exceptions None
>
> r it says,*
> ntimeError: IOError: [Errno 2] No such file or directory: '/tmp/beam-temp-py-wordcount-direct-7013276afc6311e8a71108002721555c/72786d7f-a2b4-461c-91fa-c7e04d55ea3a.py-wordcount-direct' [while running 'write/Write/WriteImpl/WriteBundles']
>
>

Imported from Jira [BEAM-6259](https://issues.apache.org/jira/browse/BEAM-6259). Original Jira may contain additional context.
Reported by: morvenhuang.