Sudo apt-get -y install python-virtualenv virtualenv :
All the programs are ok installed in the last version.

I reinstalled python.

Still the same error.
Sentinell is not installed.

Not big issue : the masternode reward is still ok, despite the watchdog expired message.

Edit :
The installation script send me messages in the /var/mail directory : it seems there is a path issue : "/bin/sh: 1: cd: can't cd to /home/camille/sentinel
"