Activiti: Shell Task freezes process when it used Python

Question

Question about Activiti 5.17.0.

I'm researching to use external REST API and thought Shell Task with Python might be good solution. But it freezes the process in Activiti Explorer. Is there any better way?

Read manual here: (Shell Task)

http://www.activiti.org/userguide/#bpmnShellTask

Found working sample:

https://github.com/Activiti/Activiti/blob/master/modules/activiti-engine/src/test/resources/org/activiti/examples/bpmn/shell/ShellTaskTest.testEchoShellWindows.bpmn20.xml

It works simple Windows command (ex. echo), but using Python freezes the process and browser.

It waits process done forever (or until timeout). Browser shows waiting icon and do not respond in Activiti Explorer.

It works as following:

• OK: simple DOS command
• OK: simple batch file
• OK: batch file in batch file (note: don't use "call")

Followings are not working and causes freeze:

• NG: python (even --version)
• NG: batch file call python
• NG: batch file call another batch file with "call" command

I've tried "wait" option (default=true) as false. Then process comes back, but there's no result value evaluated.

Is there any workaround or better solution to use external REST API from Activiti? Any advice is helpful.

Thank you, Naoki