Even when you use a text file containing the XML provided by export workspace,
you get an error.  Here is the traceback:

Site Error

An error was encountered while publishing this resource.

BadRequest

Sorry, a site error occurred.
Traceback (innermost last):

Module ZPublisher.Publish, line 188, in publish_module_standard
Module ZPublisher.Publish, line 145, in publish
Module Zope2.App.startup, line 222, in zpublisher_exception_hook
Module ZPublisher.Publish, line 114, in publish
Module ZPublisher.mapply, line 88, in mapply
Module ZPublisher.Publish, line 40, in call_object
Module Products.SGDI.SGDI, line 1052, in importWorkspace
Module Products.SGDI.SGDI, line 989, in addWorkspace
Module Products.SGDI.SGDIworkspace, line 16, in manage_addSGDIworkspace
Module Products.SGDI.SGDIworkspace, line 30, in __init__
Module OFS.Image, line 57, in manage_addFile
Module OFS.ObjectManager, line 297, in _setObject
Module OFS.ObjectManager, line 73, in checkValidId
BadRequest: ('Empty or invalid id specified', '') (Also, the following error
occurred while attempting to render the standard error message, please see the
event log for full details: You are not allowed to access 'title_or_id' in this
context)