launchpad snap recipe fails with classic confinement

[knitzsche]

Is building a snap with *classic* confinement from a recipe supported on lp?

I created a snap recipe for my imported git branch and tried to build, 
and the builds fail with:

Preparing to pull env
classic confinement requires the core snap to be installed. Install it 
by running `snap install core`.
Traceback (most recent call last):
   File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 199, in main
     builder.pull()
   File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 136, in pull
     env=env)
   File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 92, in 
run_build_command
     self.chroot(["/bin/sh", "-c", command], echo=echo)
   File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 66, in chroot
     "/usr/bin/sudo", "/usr/sbin/chroot", self.chroot_path] + args)
   File "/usr/lib/python2.7/subprocess.py", line 541, in check_call
     raise CalledProcessError(retcode, cmd)
CalledProcessError: Command '['/usr/bin/sudo', '/usr/sbin/chroot', 
'/home/buildd/build-SNAPBUILD-21071/chroot-autobuild', 'linux32', 
'/bin/sh', '-c', 'cd /build/make-system-user && env LANG=C.UTF-8 
https_proxy=http://snap-proxy.launchpad.net:3128 
http_proxy=http://snap-proxy.launchpad.net:3128 
SNAPCRAFT_LOCAL_SOURCES=1 snapcraft pull']' returned non-zero exit status 1


cheers,
kyleN