Warnings during runs of core:archive will always cause it to exit with an exit code of 1, even if the task didn't encounter any errors:

Error: error or warning logs detected, exit 1

This behavior is not helpful and IMO unexpected. *nix programs usually only return a non-zero return code when the operation requested by the user failed entirely. core:archive's current behavior makes it unreasonably complicated to decide whether it failed or not; a script that reports errors to an administrator by mail would have to parse core:archive's output to make that decision.

It would be very helpful if this behavior was either removed entirely, or if it could be disabled with a flag.