No idea, however.. I resolved that via a bash script...
vicm3@f:~$ more creaplanet.sh
python planet.py linux/config.ini
For some unknow reason (at least for me) planet don't get the right path, but the script yes.
Try... to put your planet on a script and test (you can see, first I change to my own home, then to planet directory and then execute planet with his config path), as it work for me I don't try further but maybe an absolute config path would work.