If you get during an update to TYPO3 12 the following error messages: „Something went wrong clearing caches“ or „Something went wrong, The request was not processed successfully“

Solution

The solution is quite simple but hard to find. In a sitepackage or another extension usually php-files start with the following code:

<?php
defined('TYPO3_Mode') || die();

„TYPO3_Mode“ is deprecated the new correct statement is with just „TYPO3″_

<?php
defined('TYPO3') || die();

The frontend in my case also produced just a white page so it was very hard to find the problem.

More information is found here:

https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/11.0/Deprecation-92947-DeprecateTYPO3_MODEAndTYPO3_REQUESTTYPEConstants.html