FileManager.Import error when called a second time in automation

Steps to reproduce :

• Have a handler for "document created" for File
• In this handler, call FileManager.Import to create another document
• Depoy on your server and upload a File
• The server displays an error (see server.log.txt ):

  [org.nuxeo.ecm.webengine.app.WebEngineExceptionMapper] org.nuxeo.ecm.core.api.NuxeoException: Failed to invoke operation FileManager.Import, Cannot use closed connection handle: org.nuxeo.ecm.core.storage.sql.ra.ConnectionImpl@67ac9b5b
  

• In the UI, cancel the dialog => the files are not displayed (look like they were not created), but refresh the UI and here they are (see )

In the "NXP-28534" branch of the targuillere-SANDBOX, you can find an automation that will help you reproduce (File_Created event handler and File_Created automation script).

Now, as described it may look as "just" a UI bug since the files are created. But this bug broke our Claim demo, where a user uploads an image to their personal workspace (via the mobile app). In the "documentCreated" event, a Claim (Folderish) is then automatically created, and at the end of the process, the file is moved inside the Claim. During the processing we called FileManager.Import to create another file in the Claim. So, when this bug occurred, the image is not moved, it stays in the personal workspace, no claim is created etc. It ruins the demo

I believe the bug was introduced in a HF starting at HF16 or 17, because I did run our Claim demo a fair amount of time last year (including December) without issues.