The goal is to have clearer failure message by distinguishing
failures (only import, import and export, only export).

Change-Id: Ic4fc5f7bfd7c9ddb0705597c3fb994e41d04b5ba
Reviewed-on: https://gerrit.libreoffice.org/6289Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>