Consistent downloading-core-snap build errors with Launchpad

I’ve been trying to build a new dmd snap package version in launchpad, and have consistently got failing builds:

As far as I can see from the build logs, e.g.:

… the problem comes when trying to download the core snap:

Downloading core
HTTPSConnectionPool(host='', port=443): Max retries exceeded with url: /api/v1/snaps/download/99T7MUlRhtI3U0QFgl5mXXESAiSwt776_2312.snap (Caused by ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 403 Forbidden',)))
Traceback (most recent call last):
  File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 243, in main
  File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 180, in pull
  File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 100, in run_build_command
    ["/bin/sh", "-c", command], echo=echo, get_output=get_output)
  File "/usr/share/launchpad-buildd/slavebin/buildsnap", line 71, in chroot
  File "/usr/lib/python2.7/", line 541, in check_call
    raise CalledProcessError(retcode, cmd)
CalledProcessError: Command '['/usr/bin/sudo', '/usr/sbin/chroot', '/home/buildd/build-SNAPBUILD-55206/chroot-autobuild', 'linux64', '/bin/sh', '-c', 'cd /build/dmd-2.075 && env LANG=C.UTF-8 https_proxy= SNAPCRAFT_LOCAL_SOURCES=1 SNAPCRAFT_SETUP_CORE=1 http_proxy= GIT_PROXY_COMMAND=/usr/local/bin/snap-git-proxy snapcraft pull']' returned non-zero exit status 1

Can anyone shed any light on what’s going on here? (Since the error is 403 Forbidden, I should note that I initially selected the wrong owner for the snap package, though it is now correct.)

Don’t know what changed, but things are now working, it seems …