The updater should disable DISPLAY_ERRORS

[veltsumatti]

If DISPLAY_ERRORS = On in php.ini, the updater process stops at phase 10.

See https://discuss.phplist.org/t/automatic-update-from-3-6-2-to-3-6-3-fails/7546

[michield]

Presumably resolved with phpList/updater#89

Should make it to the next release

Also, in general it's best to only have display errors on when developing.