Comment 3 for bug 1616831

Here is a simple recreate
$ cat > /tmp/my.user-data <<"EOF"
#cloud-config
apt:
  preserve_sources_list: false
  primary:
  - arches: [default]
    uri: http://us.archive.ubuntu.com/ubuntu
  proxy: http://192.168.122.1:8000/
  security:
  - arches: [default]
    uri: http://us.archive.ubuntu.com/ubuntu
  sources:
    launchpad_3: {source: 'deb http://ppa.launchpad.net/maas/next/ubuntu main'}

apt_proxy: http://192.168.122.1:8000/

system_info:
  package_mirrors:
  - arches: [i386, amd64]
    failsafe:
      primary: 'http://archive.ubuntu.com/ubuntu'
      security: 'http://security.ubuntu.com/ubuntu'
    search:
      primary: ['http://us.archive.ubuntu.com/ubuntu']
      security: ['http://us.archive.ubuntu.com/ubuntu']
  - arches: [default]
    failsafe:
      primary: 'http://ports.ubuntu.com/ubuntu-ports'
      security: 'http://ports.ubuntu.com/ubuntu-ports'
    search:
      primary: ['http://ports.ubuntu.com/ubuntu-ports']
      security: ['http://ports.ubuntu.com/ubuntu-ports']
EOF

$ lxc launch ubuntu-daily:yakkety "--config=user.user-data=$(cat /tmp/my.user-data)"