The build-appliance image uses poky but it should use bitbake-setup instead.
Ross to deal with the lack of poky ONLY, as an initial step, probably without using bitbake-setup. There is more work to be considered about the intent of the build-appliance but that should be tracked in separate bugs.
The separate bug is filed now: https://bugzilla.yoctoproject.org/show_bug.cgi?id=16016.
Posted 'build-appliance-image: install bitbake+oe-core+meta-yocto, not poky'.
Fixed in oe-core 57dbe13f87cc2cfc87ed12dcca12382ba710be94.