ci: sheldon enters infinite loop when Licence.txt is absent

Summary

Sheldon looks for a Licence.txt file in the directory. If there is none, it looks enters an infinity loop and gets stuck.

Steps to reproduce

Apply sheldon on a project without Licence.txt

Possible fixes

The endless loop is a while(true)... Investigate while the condition is never met. Michaël proposal: add a counter, and print log error when counter exceeded, saying that Licence.txt file should be set at the project root.