openstack undercloud upgrade fails - ValueError: No JSON object could be decoded

Issue

dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 ----------------------- PROFILING -----------------------                      [29/1961]
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 Target: install.d
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 Script                                     Seconds
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 ---------------------------------------  ----------
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 02-puppet-stack-config                        0.611
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 10-hiera-yaml-symlink                         0.005
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 10-puppet-stack-config-puppet-module          0.007
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 11-create-template-root                       0.150
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 75-puppet-modules-package                     0.010
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 99-install-config-templates                   0.154
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 99-os-refresh-config-install-scripts          0.059
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 --------------------- END PROFILING ---------------------
INFO: 2018-12-17 07:41:34,376 -- ############### End stdout/stderr logging ###############
INFO: 2018-12-17 07:41:34,376 --   Running hook post-install
INFO: 2018-12-17 07:41:34,377 --     Skipping hook post-install, the hook directory doesn't exist at /tmp/tmpttdPjT/post-install.d
INFO: 2018-12-17 07:41:34,381 -- Ending run of instack.
Instack completed successfully
Running os-refresh-config
[2018-12-17 07:41:34,459] (os-refresh-config) [INFO] Starting phase configure
dib-run-parts Mon Dec 17 07:41:34 AEDT 2018 Running /usr/libexec/os-refresh-config/configure.d/20-os-apply-config
Traceback (most recent call last):
  File "/bin/os-apply-config", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/os_apply_config/apply_config.py", line 335, in main
    opts.metadata = load_list_from_json(opts.os_config_files)
  File "/usr/lib/python2.7/site-packages/os_apply_config/apply_config.py", line 319, in load_list_from_json
    json_obj = json.loads(ocf.read())
  File "/usr/lib64/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib64/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib64/python2.7/json/decoder.py", line 384, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded
[2018-12-17 07:41:34,628] (os-refresh-config) [ERROR] during configure phase. [Command '['dib-run-parts', '/usr/libexec/os-refresh-$onfig/configure.d']' returned non-zero exit status 1]

[2018-12-17 07:41:34,629] (os-refresh-config) [ERROR] Aborting...
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/instack_undercloud/undercloud.py", line 1257, in install
    _run_orc(instack_env)
  File "/usr/lib/python2.7/site-packages/instack_undercloud/undercloud.py", line 1021, in _run_orc
    _run_live_command(args, instack_env, 'os-refresh-config')
  File "/usr/lib/python2.7/site-packages/instack_undercloud/undercloud.py", line 519, in _run_live_command
    raise RuntimeError('%s failed. See log for details.' % name)
RuntimeError: os-refresh-config failed. See log for details.
Command 'instack-install-undercloud' returned non-zero exit status 1