nocloud network-config mishandles empty config

[Ryan Harper]

root@e1:~# cat /var/lib/cloud/seed/nocloud-net/network-config
version: 1
config: []

This causes this stacktrace:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 653, in status_wrapper
    ret = functor(name, args)
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 362, in main_init
    init.apply_network_config(bring_up=bool(mode != sources.DSMODE_LOCAL))
  File "/usr/lib/python3/dist-packages/cloudinit/stages.py", line 706, in apply_network_config
    return self.distro.apply_network_config(netcfg, bring_up=bring_up)
  File "/usr/lib/python3/dist-packages/cloudinit/distros/__init__.py", line 178, in apply_network_config
    dev_names = self._write_network_config(netconfig)
  File "/usr/lib/python3/dist-packages/cloudinit/distros/debian.py", line 114, in _write_network_config
    return self._supported_write_network_config(netconfig)
  File "/usr/lib/python3/dist-packages/cloudinit/distros/__init__.py", line 93, in _supported_write_network_config
    renderer.render_network_config(network_config)
  File "/usr/lib/python3/dist-packages/cloudinit/net/renderer.py", line 56, in render_network_config
    templates=templates, target=target)
  File "/usr/lib/python3/dist-packages/cloudinit/net/netplan.py", line 202, in render_network_state
    content = self._render_content(network_state)
  File "/usr/lib/python3/dist-packages/cloudinit/net/netplan.py", line 236, in _render_content
    if network_state.version == 2:
AttributeError: 'NoneType' object has no attribute 'version'

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: cloud-init 19.2-36-g059d049c-0ubuntu3
ProcVersionSignature: Ubuntu 4.15.0-64.73~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-64-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
Date: Wed Nov 13 21:44:48 2019
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=C.UTF-8
SourcePackage: cloud-init
UpgradeStatus: No upgrade log present (probably fresh install)
cloud-init-log-warnings:
 2019-11-13 21:39:21,144 - util.py[WARNING]: failed stage init-local
 AttributeError: 'NoneType' object has no attribute 'version'
user_data.txt:
 #cloud-config
 manage_etc_hosts: localhost
 ssh_authorized_keys:
 - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDeShzUvzOCPWKyfRt0IsiO4//nyDwe6JgL0ZTHO+Wq1nRsuwysdoX9sAMlhAdgx3q6qbJu6Xa3ug1c4rqyszBBovsoOieF4ZzZzrPV4ekzzAaPB5jqCIRostiIimTnxOrnyRtdZ0F81q1jzL9SfyzlzhIVYvdcleEE8c2ziaNZfAeL/cD9MB9jCcxRTNuMQw27QE2yQ4na2YAm3tB0l6vDfiLIx9hstgwyj13I5VsFcoHNohyN0R+Fq6/Zz5rOHiUieiMcs0+b/khnfYKuqygQRpPWAl35OVJUSUgVnbRQsM9TstOfy5IxFxI5oBtueVX1ZUp/xibsZo/1V3dJkKet rharper@brettanomyces

[Ryan Harper (raharper)]

https://github.com/canonical/cloud-init/pull/45

[Launchpad Janitor (janitor)]

This bug was fixed in the package cloud-init - 19.3-74-g129b1c4e-0ubuntu1

---------------
cloud-init (19.3-74-g129b1c4e-0ubuntu1) focal; urgency=medium

  * New upstream snapshot.
    - azure: avoid re-running cloud-init when instance-id is byte-swapped
      (#84) [AOhassan]
    - fix unlocking method on FreeBSD [Igor Galić] (LP: #1854594)
    - debian: add reference to the manpages [Joshua Powers]
    - ds_identify: if /sys is not available use dmidecode (#42)
      [Igor Galić] (LP: #1852442)
    - docs: add cloud-id manpage [Joshua Powers]
    - docs: add cloud-init-per manpage [Joshua Powers]
    - docs: add cloud-init manpage [Joshua Powers]
    - docs: add additional details to per-instance/once [Joshua Powers]
    - Merge pull request #96 from fred-lefebvre/master [Joshua Powers]
    - Update doc-requirements.txt [Joshua Powers]
    - doc-requirements: add missing dep [Joshua Powers]
    - Merge pull request #95 from powersj/docs/bugs [Joshua Powers]
    - dhcp: Support RedHat dhcp rfc3442 lease format for option 121 (#76)
      [Eric Lafontaine] (LP: #1850642)
    - network_state: handle empty v1 config (#45) (LP: #1852496)
    - Merge pull request #94 from gaughen/patch-1 [Joshua Powers]
    - docs: fix line length and remove highlighting [Joshua Powers]
    - docs: Add security.md to readthedocs [Joshua Powers]
    - Multiple file fix for AuthorizedKeysFile config (#60) [Eduardo Otubo]
    - Merge pull request #88 from OddBloke/travis [Joshua Powers]
    - doc: update links on README.md [Joshua Powers]
    - doc: Updates to wording of README.md [Joshua Powers]
    - Add security.md [Joshua Powers]
    - setup.py: Amazon Linux sets libexec to /usr/libexec (#52)
      [Frederick Lefebvre]

 -- Chad Smith <email address hidden> Thu, 12 Dec 2019 16:05:35 -0700