fix(setup): update python install

README.md

@@ -15,6 +15,11 @@ Firstly you need to export some environment variables in your working terminal t
 export https_proxy=http://proxy.polytech-lille.fr:3128
 ```
 
+Also, depending on the operating system installed on your virtual machines (Ubuntu server should not have the issue, Debian might), you should install python 3:
+```
+# apt install python3
+```
+
 ### The virtualenv
 
 Since Ansible is written in python and we don't want to install it in the system, you will need to create a virtual environment. These are used to have your python stuff installed, without making them available system-wide, we are doing this to avoid polluting your lab machine with things that won't be used after today.