Update: with the latest spread things are working fine again
Currently the autopkgtests are all broken.
It appears that the error is 2017/04/03 11:32:03 Discarding autopkgtest:ubuntu-16.04-amd64, cannot connect: cannot connect to autopkgtest:ubuntu-16.04-amd64: ssh: must specify HostKeyCallback
.
Further investigation indicates that https://go-review.googlesource.com/c/38701/ is responsible.
PR for spread https://github.com/snapcore/spread/pull/28
Test run with snapd: https://github.com/snapcore/snapd/pull/3127