[modeller_usage] error: Py_InitModule4_64

Hi,

I have installed Modeller 9.13 (downloaded 
http://salilab.org/modeller/9.13/modeller-9.13.tar.gz and executed the 
Install file).
Next, I created a shared library for a user defined constraint as follows:

gcc -shared -Wall -fPIC .../bin/modeller9.13/bin/mod9.13 --cflags 
--libs` `pkg-config --cflags glib-2.0` -I/usr/include/pythonXXX my_rsr.c 
my_rsr_wrap.c -o _my_rsr.so -lm

where XXX stands for different python versions I tried (e.g. 2.5,2.6,2.7)

When executing my python script via:

...bin/modeller9.13/bin/mod9.13  my_script.py
or ...bin/modeller9.13/bin/modpy.sh pythonXXX  my_script.py

I always get the error:

ImportError: .../bin/modeller9.13/modlib/modeller/_my_rsr.so: undefined 
symbol: Py_InitModule4_64

I tried to set the python path, but it didn't help.

How can I fix this?