When using a ScriptTrigger in a free-style software project AND using slave nodes, an IOException is raised.
This seems to be caused by lines 117-118 in ScriptTriggerExecutor.java, where the closure has a reference to the LocalLauncher, which prevents the Callable from being serialized.

Scenario:

• Go to 'Jenkins', 'Manage Jenkins', 'Manage Nodes', 'New node'
  • Name the node "ScriptTrigger_node", choose 'Dumb slave', OK.
  • Set:
    • the # of executor to 1,
    • the remote FS root to a temporary directory.
    • labels to ScriptTrigger_slave
    • Launch method to "Launch slave agents via Java Web Start"
    • Save
    • Click "Launch"
• Go to 'New Job', choose "Build a free-style software project".
  • Check "Restrict where this project can be run", set labels to "ScriptTrigger_slave"
  • Check "[ScriptTrigger] - Poll with a shell or batch script".
    • I used echo "Test" >> test.txt as a script.
    • I set the schedule to * * * * *