When maintenance mode is enabled the archiver should not start and also not start working on a next website.
On top we could throw an exception in
archiveReportsFor() but AFAIK the request will fail anyway since the API will basically return an error. And in
archiveReportsFor() should not be like a
if (maintenanceEnabled) return because it could result in random bugs as we might set some flags like the site was considered archived. If we want to avoid sending requests eg in
archiveReportsFor() we should throw an exception instead like
if (maintenanceEnabled) throw new Exception('Maintenance mode is enabled') so the core archiver will stop.
Feel free to tweak messages.
LGTM :+1: Just need to wait for tests to be green
failing ui tests https://builds-artifacts.piwik.org/piwik/piwik/archivemaintenance/25251/
are not related to this change.