output of nova-api logs:

2016-03-11 11:14:36.473 19261 INFO nova.osapi_compute.wsgi.server [req-888b9029-31b6-4273-9321-d7e322e5f09e bf168041f9c5446b81bca4d737f547e7 a86464f29aac4ec5848fb481e6362fcb - - -] 10.123.35.173 "GET /v2/ HTTP/1.1" status: 200 len: 573 time: 0.0317960
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions [req-8163730d-c0c4-4dec-9d55-e69442e0888e bf168041f9c5446b81bca4d737f547e7 a86464f29aac4ec5848fb481e6362fcb - - -] Unexpected exception in API method
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions Traceback (most recent call last):
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/nova/api/openstack/extensions.py", line 478, in wrapped
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     return f(*args, **kwargs)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/nova/api/openstack/compute/images.py", line 145, in detail
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     **page_params)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/nova/image/api.py", line 68, in get_all
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     return session.detail(context, **kwargs)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/nova/image/glance.py", line 284, in detail
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     for image in images:
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/v1/images.py", line 254, in list
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     for image in paginate(params, return_request_id):
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/v1/images.py", line 238, in paginate
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     images, resp = self._list(url, "images")
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/v1/images.py", line 63, in _list
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     resp, body = self.client.get(url)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/common/http.py", line 280, in get
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     return self._request('GET', url, **kwargs)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/common/http.py", line 272, in _request
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     resp, body_iter = self._handle_response(resp)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions   File "/usr/lib/python2.7/site-packages/glanceclient/common/http.py", line 93, in _handle_response
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions     raise exc.from_response(resp, resp.content)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions HTTPInternalServerError: 500 Internal Server Error: The server has either erred or is incapable of performing the requested operation. (HTTP 500)
2016-03-11 11:14:36.680 19261 ERROR nova.api.openstack.extensions
2016-03-11 11:14:36.681 19261 INFO nova.api.openstack.wsgi [req-8163730d-c0c4-4dec-9d55-e69442e0888e bf168041f9c5446b81bca4d737f547e7 a86464f29aac4ec5848fb481e6362fcb - - -] HTTP exception thrown: Unexpected API Error. Please report this at http://bugs.launchpad.net/nova/ and attach the Nova API log if possible.
<class 'glanceclient.exc.HTTPInternalServerError'>
2016-03-11 11:14:36.682 19261 INFO nova.osapi_compute.wsgi.server [req-8163730d-c0c4-4dec-9d55-e69442e0888e bf168041f9c5446b81bca4d737f547e7 a86464f29aac4ec5848fb481e6362fcb - - -] 10.123.35.173 "GET /v2/a86464f29aac4ec5848fb481e6362fcb/images/detail HTTP/1.1" status: 500 len: 445 time: 0.0707080