Folder not deleted on client when file is open without notification

1. Connect Drive and wait for sync completion
2. Create folder structure as below with MS word documents:
   Test/A/doc1.docx, Test/B/doc2.docx, Test/C/doc3.docx, Test/D/doc4.docx
3. Open file doc3.docx in MS Word
4. Go to select sync folders, uncheck the folder Test
5. Wait for 30 seconds and quit drive client
6. Start drive client, close the file and check the folder test in select sync folders (Make sure that Nuxeo icon is not in sync state)
7. C is not deleted because of Word has a lock on the file.
8. Observe in the logs an error, which is expected and one after several attempts in the UI.

Desired behavior: a notification should be displayed to the user so that he knows the folder cannot be deleted until the lock has been removed (i.e. closing Word)