If you encounter error during pysam installation:
[bash]
sudo easy_install -U pysam

…

pysam/csamtools.c:8:22: fatal error: pyconfig.h: No such file or directory
#include "pyconfig.h"
^
compilation terminated.
error: Setup script exited with error: command ‘x86_64-linux-gnu-gcc’ failed with exit status 1
[/bash]

try installing python-dev first.
[bash]
sudo apt-get install python-dev
[/bash]

Solution found on github.