Upgrade bug

Having problems installing Concrete CMS?

I got the following message when trying to upgrade to the llastest concretecms version.

Target [PsrExt\Log\LoggerInterface] is not instantiable while building [Concrete\Core\Foundation\Runtime\Run\DefaultRunner, Concrete\Core\Cache\CacheClearer].

The dashboard and the site are now inaccessible. Looking for someone who got the same issue and / or who can help me solving the issue.