Error when getting appliance info

[enolfc]

Short Description of the issue

v0.11.4 fails at CESNET-MCC when trying to get appliance info:

Traceback (most recent call last):
  File "/usr/local/bin/cloud-info-provider-service", line 10, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/core.py", line 120, in main
    mgr.driver.format(opts, providers, auth_refresher)
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/formatters/base.py", line 50, in format
    info = available_collectors[tpl].fetch()
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/collectors/compute.py", line 37, in fetch
    **kwargs)
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/collectors/base.py", line 25, in _get_info_from_providers
    result = getattr(i, method)(**provider_kwargs)
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/providers/openstack.py", line 51, in inner
    return f(self, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/cloud_info_provider/providers/openstack.py", line 309, in get_images
    extra_attrs = json.loads(image.get('APPLIANCE_ATTRIBUTES', '{}'))
  File "/usr/local/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/usr/local/lib/python2.7/json/decoder.py", line 364, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/local/lib/python2.7/json/decoder.py", line 382, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded