Custom taxonomy must be registerd in the themes functions.php in order to import the terms

[design_dolphin]

It appears that the taxonomy must be registered in the theme functions.php in order to import the terms.

Proposed solution:

A warning message that if custom taxonomy is detected in the import file advising the user to first register any and all custom taxonomies in the theme before being able to continue with import.

[nacin]

Closing #13453 as a duplicate.

[design_dolphin]

This is not a duplicate. :-) They are separate issues.

[nacin]

This is not something we're going to get to in a point release.

I also find this to be an enhancement -- if the taxonomy isn't registered, there isn't much we can do. If all we're going to do is add a warning message, then that is simply enhancing existing behavior.

[nacin]

(In [15961]) Importer and exporter overhaul, mega props duck.

Exporter overhaul:

• Add author information to export
• Greater usage of slug identifiers
• Don't export auto-drafts, spam comments, or edit lock/last meta keys
• Inline documentation improvements
• Remove filtering for now (@todo)
• Bump WXR version to 1.1, but remain back compat in the importer

Importer overhaul (​http://plugins.trac.wordpress.org/changeset/304249):

• Use an XML parser where available (SimpleXML, XML Parser)
• Proper import support for navigation menus
• Many bug fixes, specifically improvements to category and custom taxonomy handling
• Better author/user mapping

Fixes #5447 #5460 #7400 #7973 #8471 #9237 #10319 #11118 #11144 #11354 #11574 #12685 #13364 #13394 #13453 #13454 #13627 #14306 #14442 #14524 #14750 #15055 #15091 #15108.

See #15197.