deskutils/gucharmap fails to build - why?

[Torfinn Ingolfsen]

deskutils/gucharmap fails to install / build with:
Traceback (most recent call last):
  File "/usr/local/bin/xml2po", line 35, in <module>
    import libxml2
ImportError: No module named libxml2
gmake[2]: *** [bg/gucharmap.xml] Error 1
gmake[2]: Leaving directory
`/usr/ports/deskutils/gucharmap/work/gucharmap-2.26.3.1/help'
gmake[1]: *** [all-recursive] Error 1
gmake[1]: Leaving directory
`/usr/ports/deskutils/gucharmap/work/gucharmap-2.26.3.1'
gmake: *** [all] Error 2
*** Error code 1

Stop in /usr/ports/deskutils/gucharmap.
** Command failed [exit code 1]: /usr/bin/script -qa
/tmp/portinstall20090810-90423-sq9drr-0 env make
** Fix the problem and try again.
** Listing the failed packages (-:ignored / *:skipped / !:failed)
    ! deskutils/gucharmap    (unknown build error)

But why does it do that?
libxml2 is installed:
root at kg-v2# portversion -Ov | grep libxml2
libxml2-2.7.3               =  up-to-date with port
linux-f8-libxml2-2.7.2_2    =  up-to-date with port
py26-libxml2-2.7.3          =  up-to-date with port

This is on a machine running:

root at kg-v2# uname -a
FreeBSD kg-v2.kg4.no 7.2-STABLE FreeBSD 7.2-STABLE #0: Fri Jul 17 18:23:22
CEST 2009     root at kg-v2.kg4.no:/usr/obj/usr/src/sys/V2  amd64

with the ports tree updated today.
-- 
Regards,
Torfinn Ingolfsen