a user trying to synchronize an invalid package needs a user-friendly error message
A user (inadvertently) created an invalid package (see bug #3978), and attempted to save it to the network. When file ->save did not work, she tried file -> synchronize.
there was no error message, but a very long string appeared that included an XPath. An IM was able to discern from this what the document's problem was, but this is not appropriate for anyone unfamiliar with XML.