After some research, why not simply use 
````Python 
import platform
platform.linux_distribution()
````
For all Linux OS ? 

It returns for a 

CentOS : 
````Python 
('CentOS', '6.4', 'Final')
````
Debian : 
````Python 
('debian', '6.0.7', '')
````

Work well, but we have to check first the version of Python because in python < 2.6 we have to use platform.dist
Something like : 

````Python 
try:
    import platform.linux_distribution as dist  # Python > 2.6
except: import platform.dist as dist  # Python < 2.6

dist()
````