NervesPack 0.4.0 is a minor bump with a fairly big change.
This update drops :nerves_firmware_ssh in favor of the newer and more focused libraries NervesSSH and SSHSubsystemFwup.
Upgrading existing projects using NervesPack may require a few changes to get working properly. See the Upgrading from NervesFirmwareSSH notes for helpful steps on that.
You may also want to update your local nerves_bootstrap archive to >= 1.9.0 so that any new Nerves project generated with mix nerves.new will have this update as well:
mix local.nerves
You can read more about NervesSSH in the release announcement or the documentation
