The error is not in your Chevereto installation but in the PHP setup of your machine. The system is trying to detect if folder at /install exists, for Chevereto the path to check is at /home/alexwilliamfr/webapps/install (detected at runtime with $_SERVER variables).
The problem is your PHP setup as your allowed paths for open_basedir are:
As you may notice, the document root detected (/home/alexwilliamfr/webapps/) is not within these paths, most likely your hosting is not providing the right configuration either at configuring the allowed paths or at the reported runtime path.