Description of problem:
While verifying the RFE, Bug 979142 , I've tried to add a location of the existing image, according the commands in the test case https://tcms.engineering.redhat.com/run/87718/#caserun_3433837 . 

The test: add 2nd location (localFS) failed. 

The glance API log show: 

2013-11-06 15:21:45.973 6953 DEBUG glance.api.middleware.version_negotiation [-] Determining version of request: PATCH /v2/images/149563cb-0ad5-4bcc-a933-a24744219e53 Accept: */* process_request /usr/lib/python2.6/site-packages/glance/api/middleware/version_negotiation.py:46
2013-11-06 15:21:45.979 6953 DEBUG glance.api.middleware.version_negotiation [-] Using url versioning process_request /usr/lib/python2.6/site-packages/glance/api/middleware/version_negotiation.py:59
2013-11-06 15:21:45.979 6953 DEBUG glance.api.middleware.version_negotiation [-] Matched version: v2 process_request /usr/lib/python2.6/site-packages/glance/api/middleware/version_negotiation.py:71
2013-11-06 15:21:45.979 6953 DEBUG glance.api.middleware.version_negotiation [-] new path /v2/images/149563cb-0ad5-4bcc-a933-a24744219e53 process_request /usr/lib/python2.6/site-packages/glance/api/middleware/version_negotiation.py:72
2013-11-06 15:21:45.980 6953 DEBUG keystoneclient.middleware.auth_token [-] Authenticating user token __call__ /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:558
2013-11-06 15:21:45.980 6953 DEBUG keystoneclient.middleware.auth_token [-] Removing headers from request environment: X-Identity-Status,X-Domain-Id,X-Domain-Name,X-Project-Id,X-Project-Name,X-Project-Domain-Id,X-Project-Domain-Name,X-User-Id,X-User-Name,X-User-Domain-Id,X-User-Domain-Name,X-Roles,X-Service-Catalog,X-User,X-Tenant-Id,X-Tenant-Name,X-Tenant,X-Role _remove_auth_headers /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:617
2013-11-06 15:21:45.993 6953 INFO urllib3.connectionpool [-] Starting new HTTP connection (1): 10.35.160.113
2013-11-06 15:21:46.168 6953 DEBUG urllib3.connectionpool [-] "POST /v2.0/tokens HTTP/1.1" 200 6203 _make_request /usr/lib/python2.6/site-packages/urllib3/connectionpool.py:295
2013-11-06 15:21:46.182 6953 INFO urllib3.connectionpool [-] Starting new HTTP connection (1): 10.35.160.113
2013-11-06 15:21:46.220 6953 DEBUG urllib3.connectionpool [-] "GET /v2.0/tokens/revoked HTTP/1.1" 200 794 _make_request /usr/lib/python2.6/site-packages/urllib3/connectionpool.py:295
2013-11-06 15:21:46.247 6953 DEBUG keystoneclient.middleware.auth_token [-] Storing d57816aeebd4ade336c6505a20e6ec78 token in memcache _cache_put /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:1061
2013-11-06 15:21:46.249 6953 DEBUG keystoneclient.middleware.auth_token [-] Received request from user: c7fdf6f628554d56aad363ad501ce412 with project_id : add3de2deaa445c1a1e71c1721bc8976 and roles: admin  _build_user_headers /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:922
2013-11-06 15:21:46.252 6953 DEBUG routes.middleware [-] Matched PATCH /images/149563cb-0ad5-4bcc-a933-a24744219e53 __call__ /usr/lib/python2.6/site-packages/Routes-1.12.3-py2.6.egg/routes/middleware.py:100
2013-11-06 15:21:46.252 6953 DEBUG routes.middleware [-] Route path: '/images/{image_id}', defaults: {'action': u'update', 'controller': <glance.common.wsgi.Resource object at 0x31c99d0>} __call__ /usr/lib/python2.6/site-packages/Routes-1.12.3-py2.6.egg/routes/middleware.py:102
2013-11-06 15:21:46.252 6953 DEBUG routes.middleware [-] Match dict: {'action': u'update', 'image_id': u'149563cb-0ad5-4bcc-a933-a24744219e53', 'controller': <glance.common.wsgi.Resource object at 0x31c99d0>} __call__ /usr/lib/python2.6/site-packages/Routes-1.12.3-py2.6.egg/routes/middleware.py:103
2013-11-06 15:21:46.273 6953 DEBUG glance.api.policy [d88960b1-2e7a-4223-9b99-92abd4b20e50 c7fdf6f628554d56aad363ad501ce412 add3de2deaa445c1a1e71c1721bc8976] Loaded policy rules: {u'context_is_admin': 'role:admin', u'default': '@', u'manage_image_cache': 'role:admin'} load_rules /usr/lib/python2.6/site-packages/glance/api/policy.py:75
2013-11-06 15:21:46.288 6953 DEBUG glance.api.policy [d88960b1-2e7a-4223-9b99-92abd4b20e50 c7fdf6f628554d56aad363ad501ce412 add3de2deaa445c1a1e71c1721bc8976] Loaded policy rules: {u'context_is_admin': 'role:admin', u'default': '@', u'manage_image_cache': 'role:admin'} load_rules /usr/lib/python2.6/site-packages/glance/api/policy.py:75
2013-11-06 15:21:46.289 6953 DEBUG glance.api.policy [d88960b1-2e7a-4223-9b99-92abd4b20e50 c7fdf6f628554d56aad363ad501ce412 add3de2deaa445c1a1e71c1721bc8976] Loaded policy rules: {u'context_is_admin': 'role:admin', u'default': '@', u'manage_image_cache': 'role:admin'} load_rules /usr/lib/python2.6/site-packages/glance/api/policy.py:75


Version-Release number of selected component (if applicable):
openstack-glance-2013.2-1.el6ost.noarch

How reproducible:
everytime

Steps to Reproduce:
1. Follow the setup case in the test case https://tcms.engineering.redhat.com/run/87718/#caserun_3433837
2. run the command: curl -i -X PATCH -H 'Content-Type: application/openstack-images-v2.1-json-patch' -H "X-Auth-Token: <RHOS user ID>" http://localhost:9292/v2/images/<image_id> -d '[{"op": "add", "path": "/locations/-", "value": {"url": "file://<path to the copy>", "metadata": {}}}]'
3.

Actual results:
the output is: 

<html>
 <head>
  <title>400 Bad Request</title>
 </head>
 <body>
  <h1>400 Bad Request</h1>
  Invalid location: file:///home/user/mycopy.img<br /><br />
 </body>


Expected results:
HTTP/1.1 200 OK
Content-Length: 595
Content-Type: application/json; charset=UTF-8
X-Openstack-Request-Id: req-4958f566-66bf-4a65-8fe0-43006d2040d2
Date: Thu, 08 Aug 2013 17:25:54 GMT

{"status": "active", "name": "my_image", "tags": [], "container_format": "bare", "created_at": "2013-08-08T17:25:06Z", "disk_format": "vhd", "updated_at": "2013-08-08T17:25:54Z", "visibility": "private", "locations": [{"url": "http://cloud.fedoraproject.org/fedora-19.x86_64.qcow2", "metadata": {}}, {"url": "file:///etc/group", "metadata": {}}], "self": "/v2/images/41717c78-c926-47aa-922e-295596959e5b", "protected": false, "id": "41717c78-c926-47aa-922e-295596959e5b", "file": "/v2/images/41717c78-c926-47aa-922e-295596959e5b/file", "min_disk": 0, "min_ram": 0, "schema": "/v2/schemas/image"}

Additional info: