The egmde-snap is failing to upload to the store with:
"unknown keys in snap/manifest.yaml: snapcraft-os-release-id,snapcraft-os-release-version-id,snapcraft-version lint-snap-v2_snap_manifest"
I’ve also seen this with building mir-kiosk on Launchpad.
Is this because it builds using the 18.04 archive?
Yes, the snapcraft revert only seems to have happened for 16.04. See Builds failing automated review for more discussion.
@popey we’ve been following the usual process to update the review-tools in the store and unfortunately bumped into some unrelated issues ([SOLVED] Request failures to the store) which have pushed this rollout back a bit.
Rest assured it’s highest in our list of priorities, as soon as the fire is out (you don’t want to do a renovation on a house that’s on fire, right? 
FYI, I’m in the process of performing the same workaround I did for core16 uploads for core18, so LP/snapcraft.io uploads targeting core18 should start passing again soon.
FYI, this is done for core18 and now snap specifying ‘base: core18’ are passing automated reviews. @roadmr is working on getting the updated review-tools into production as we speak (this will help people using ‘snapcraft push’ directly).