Can't build python 3.6.4 on 6.2-current.

Hello,

while attempting to build lang/swi-prolog using dpb I've hit issue building python 3.6.4. The log
of python 3.6.4 build looks fine up to the moment of fake installation which fails with:

===> lang/python/3.6
===> Faking installation for Python-3.6.4
install -d -m 755 /usr/ports/pobj/Python-3.6.4/fake-amd64
cd /usr/ports/lang/python/3.6 && umask 022 && PKGPATH=lang/python/3.6 exec /usr/bin/make _pre-fake-modules PATH='/usr/ports/pobj/Python-3.6.4/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11R6/bin' TRUEPREFIX=/usr/local PREFIX=/usr/ports/pobj/Python-3.6.4/fake-amd64/usr/local DESTDIR=/usr/ports/pobj/Python-3.6.4/fake-amd64
Error: The source directory (/usr/ports/pobj/Python-3.6.4/Python-3.6.4) is not clean
Building Python out of the source tree (in /usr/local/ports/pobj/Python-3.6.4/Python-3.6.4) requires a clean source tree (/usr/ports/pobj/Python-3.6.4/Python-3.6.4)
Try to run: make -C "/usr/ports/pobj/Python-3.6.4/Python-3.6.4" clean
*** Error 1 in /usr/local/ports/pobj/Python-3.6.4/Python-3.6.4 (Makefile:467 'check-clean-src')
*** Error 1 in /usr/ports/lang/python/3.6 (/usr/ports/infrastructure/mk/bsd.port.mk:2837 '/usr/ports/pobj/Python-3.6.4/fake-amd64/.fake_done')
*** Error 1 in /usr/ports/lang/python/3.6 (/usr/ports/infrastructure/mk/bsd.port.mk:2419 'fake')
===> Exiting lang/python/3.6 with an error
*** Error 1 in /usr/local/ports (/usr/ports/infrastructure/mk/bsd.port.subdir.mk:147 'fake')
Error: job failed with 256 on localhost


Is it a known issue or am I doing anything stupid? Dpb was invoked as root from /usr/ports with:

./infrastructure/bin/dpb /home/karel/src/swi-prolog.txt

where cat /home/karel/src/swi-prolog.txt shows:

fujitsu# cat /home/karel/src/swi-prolog.txt
lang/swi-prolog
fujitsu#

I'm just curious since I'd like to be able to have reference ports builder here to detect any issues while hacking on OpenBSD header files...

6.2-current is from yesterday, ports tree is fresh from today.

Thanks!
Karel