TYPO3 Core

This is also the case for RteMagicImagesUpdateWizard.

I would say it is not the job of a particular UpdateWizard to tell about the log, but rather the install tool itself.

I'd propose to configure a dedicated log file to cover any logRecord which is triggered inside of typo3/sysext/install:

typo3temp/logs/install-tool.log

What do you think?

Could be added to DefaultConfiguration.php with:

'LOG' => array(
    'TYPO3' => array (
        'CMS' => array(
            'Install' => array(
                'writerConfiguration' => array(
                    \TYPO3\CMS\Core\Log\LogLevel::DEBUG => array(
                        'TYPO3\\CMS\\Core\\Log\\Writer\\FileWriter' => array(
                            'logFile' => 'typo3temp/logs/install-tool.log'
                        ),
                    ),
                ),
            ),
        ),
    ),
),

Then announce this file and the related log configuration at a prominent place in install tool.

What could be a good place for this announcement?

One could argue that adding a random suffix to the filename like deprecation_3f11ecba79.log

I think we should discuss this before.

Steffen, thanks a lot for taking care about this. Your proposal sounds great.

Prominent place would be the overview of the upgrade wizards.
I don't mind the whether we have a file suffix or not.