I verified that mwhudson's PR is sufficient for UC20 at least, provided it is changed slightly to account for the actual JSON structure. I built a core20 snap with the new python dependencies that console-conf has, and updated the things that the PR changes in the core20 snap and built a snap with the lxd, core18, snapd, pc, core20, and pc-kernel snaps seeded and I was able to use console-conf to create a user. I also verified that the lxd snap had created the lxd user entry in extrausers passwd before running console-conf and it created lxd first, verifying the fix.
I verified that mwhudson's PR is sufficient for UC20 at least, provided it is changed slightly to account for the actual JSON structure. I built a core20 snap with the new python dependencies that console-conf has, and updated the things that the PR changes in the core20 snap and built a snap with the lxd, core18, snapd, pc, core20, and pc-kernel snaps seeded and I was able to use console-conf to create a user. I also verified that the lxd snap had created the lxd user entry in extrausers passwd before running console-conf and it created lxd first, verifying the fix.