Changing default_language doesn't set siteroot.language

[jaroel]

When I change the default language in @@language-controlpanel, then the language attribute on the site root object isn't changed to reflect this.

This causes constraint errors in adding/editing DX objects when the previous default language is no longer one of the available languages.
ie, when changing the site from EN to only DE after initial setup.

Also see plone/plone.app.dexterity#258

[jaroel]

Use this in an upgrade step as a workaround:

from plone import api
pl = api.portal.get_tool('portal_languages')
default_language = pl.getDefaultLanguage()
root = api.portal.get()
root.language = default_language

[jensens]

I can confirm this, also the DX control panel does not work any longer.