Given a project using Artifact link types (aka. natures), a custom artifact link type "written_in" and a tracker with artifacts that have "written_in" artifact links
When I export the project using "export_project_xml.php"
Then the resulting XML file will miss the following information:
- missing use-natures="true" attribute on the tracker
- missing tree
<natures>
<nature>written_in</nature>
</natures>

When I try to import the attached archive on a platform where "written_in" type is not defined (you can simulate this by changing the shortname in DB), then I will not be stopped by the importer and I will have fatal errors when importing changesets (see attached logs)