During image update metadata Danger: There was an error submitting the form. Please try again.

[Eran Kuris]

Log in to horizon as Admin user Navigate to image in admin Tab
create image and then type on " update metadata"

we get error : Danger: There was an error submitting the form. Please try again.

In log file of horizon :
2015-07-21 13:35:14,607 28006 ERROR django.request Internal Server Error: /dashboard/admin/images/06b7c500-768c-4c17-abbe-7a5258674cd2/update_metadata/
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 36, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 84, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 52, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 36, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 84, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/generic/base.py", line 89, in dispatch
    return handler(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/generic/edit.py", line 215, in post
    return self.form_valid(form)
  File "/usr/lib/python2.7/site-packages/horizon/forms/views.py", line 173, in form_valid
    exceptions.handle(self.request)
  File "/usr/lib/python2.7/site-packages/horizon/exceptions.py", line 364, in handle
    six.reraise(exc_type, exc_value, exc_traceback)
  File "/usr/lib/python2.7/site-packages/horizon/forms/views.py", line 170, in form_valid
    handled = form.handle(self.request, form.cleaned_data)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/admin/images/forms.py", line 65, in handle
    _('Unable to update the image metadata.'))
  File "/usr/lib/python2.7/site-packages/horizon/exceptions.py", line 364, in handle
    six.reraise(exc_type, exc_value, exc_traceback)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/admin/images/forms.py", line 48, in handle
    new_metadata = json.loads(self.data['metadata'])
  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 365, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib64/python2.7/json/decoder.py", line 383, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

version :
[root@puma16 ~(keystone_admin)]# rpm -qa |grep horizon
python-django-horizon-2015.1.0-10.el7ost.noarch