Comment 27 for bug 1713490

For the actual change, you'd want to do this:
in qemu's debian/contol.in there are a bunch of Recommends and Depends like this:
  ipxe-qemu (>= 1.0.0+git-20131111.c3d1e78-1~)
change all those in UCA to
  ipxe-qemu (>= 1.0.0+git-20180124.fbe8c52d-0ubuntu2.1~)

That should avoid further issues with partial upgrades like this.
I never uploaded to UCA, will you do that James?