Comment 4 for bug 1692916

Validating xenial and zesty with the above script:
xenial START --------------
Creating xenial-proposed-123719471
...
The following packages will be upgraded:
  cloud-init
1 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.
Need to get 324 kB of archives.
After this operation, 44.0 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 cloud-init all 0.7.9-233-ge586fe35-0ubuntu1~16.04.1 [324 kB]
...
Valid cloud-config file /valid.conf
Valid cloud-config file /invalid.conf
...
The following NEW packages will be installed:
  python3-jsonschema
# And we now can see schema errors when jsonschema is installed
Cloud config schema errors: ntp.pools: -1 is not of type 'array'

zesty START --------------
Creating zesty-proposed-34023523
...
The following packages will be upgraded:
  cloud-init
...
Get:1 http://archive.ubuntu.com/ubuntu zesty-proposed/main amd64 cloud-init all 0.7.9-233-ge586fe35-0ubuntu1~17.04.1 [321 kB]
...
Creating test-zesty
Valid cloud-config file /valid.conf
Valid cloud-config file /invalid.conf
...
The following NEW packages will be installed:
  python3-jsonschema
# And we now can see schema errors when jsonschema is installed
Cloud config schema errors: ntp.pools: -1 is not of type 'array'