As we are reaching the Tuleap end of support of RHEL/CentOS 6, the Tuleap new default should be RHEL/CentOS 7.
The Docker image used to run the REST tests is still based on CentOS 6, it should be moved to CentOS 7.
It is also needed for
request #13487 because PHP 7.4 packages are not available on CentOS 6.