sga-astat module not found

[pnatsi]

Hello,

I am trying to run the sga pipeline, and I can't make the sga-astat work.
The error that I get is:

Traceback (most recent call last):
File "/usr/bin/sga-astat", line 6, in
import pysam
File "/usr/lib/python2.7/dist-packages/pysam/init.py", line 5, in
from pysam.libchtslib import *
ImportError: No module named libchtslib

I tried re-installing pysam many times, but couldn't fix it.
Any suggestions?