TYPO3 Core

To identify a problem it would be genius to allow error identification by a unique number :D
Therefore i suggest to add the issue information to the unavailable and page not found handlers:

Snipped from TypoScriptFrontendController :: getConfigArray 

                    if ($this->checkPageUnavailableHandler()) {
                        $this->pageUnavailableAndExit($message);
                    } else {
                        $explanation = 'This means that there is no TypoScript object of type PAGE with typeNum=' . $this->type . ' configured.';
                        \TYPO3\CMS\Core\Utility\GeneralUtility::sysLog($message, 'cms', \TYPO3\CMS\Core\Utility\GeneralUtility::SYSLOG_SEVERITY_ERROR);
                        throw new \TYPO3\CMS\Core\Error\Http\ServiceUnavailableException($message . ' ' . $explanation, 1294587217);
                    }