error: Fatal error: Class 'Drupal\syslog\Logger\SysLog' not found in /lib/Drupal/Component/DependencyInjection/Container.php on line 272 I just activated the module syslog in an almost fresh D8 install and now it has crashed. =( How do I deactivate a core module like this manually or fix the issue?
If this is a local install, you could install Drush, and then: drush dis module. Or you can go here for more sophisticated solutions.