When updating from a 5.3.4 to a 5.3.5 (following the steps from https://doc.ez.no/display/EZP/5.3.5+Release+Notes) the command to generate legacy extensions autoloads is wrong:
php ezpublish/console ezpublish:legacy:script ezpublish_legacy/bin/php/ezpgenerateautoloads.php -e
it results in an error saying the script cannot be found.
It had to be run as:
php ezpublish/console --env=prod ezpublish:legacy:script bin/php/ezpgenerateautoloads.php -e
to work (path relative to legacy root, and not ezpublish root).

Edit: Same happens on https://doc.ez.no/display/EZP/5.4.2+Release+Notes