Tvheadend

Grabber runs, grabs data, finishes:

2015-10-31 07:49:08.018 spawn: added from horizon.tv: 07 Nov 07:15 - 07:35: De Speelgoeddokter Genre: jeugd.
2015-10-31 07:49:56.471 spawn: added from horizon.tv: 07 Nov 07:35 - 07:45: Miles van Morgen Genre: jeugd.
2015-10-31 07:51:09.181 spawn: added from horizon.tv: 07 Nov 07:45 - 08:15: Jake en de Nooitgedachtland Piraten Genre: jeugd.
2015-10-31 07:51:40.281 spawn: added from horizon.tv: 07 Nov 08:15 - 08:40: Good Luck Charlie Genre: jeugd.
2015-10-31 07:52:00.346 spawn: added from horizon.tv: 07 Nov 08:40 - 09:05: Jessie Genre: jeugd.
2015-10-31 07:52:18.172 spawn: added from horizon.tv: 07 Nov 09:05 - 09:30: Liv and Maddie Genre: jeugd.
2015-10-31 07:53:44.052 /usr/bin/tv_grab_nl.py: no output detected
2015-10-31 07:53:44.052 /usr/bin/tv_grab_nl.py: grab returned no data

Why does Tvheadend not detect the output ?

There is data:

pi@tvheadend /home/hts/.xmltv $ ls l
total 66844
-rw-r--r- 1 hts video 31459328 Oct 31 07:46 program_cache.db
rw-r--r- 1 hts video 30923776 Oct 31 07:23 program_cache.db.bak
rw-rw-rw 1 hts video 26170 Oct 30 19:04 tv_grab_nl_py.conf
rw-r--r- 1 hts hts 11512 Oct 30 17:05 tv_grab_nl_py.conf.old
rw-rw-rw 1 hts video 2776165 Oct 31 07:53 tv_grab_nl_py.log
rw-rw-rw 1 hts video 3213762 Oct 31 00:31 tv_grab_nl_py.log.old
rw-rw-rw 1 hts video 14922 Oct 30 19:30 tv_grab_nl_py.set