Add list user groups api to identity v3

Identity v3 lack of list user groups, so I do the addition.
To test the addition, I add a test :
- test_list_user_groups

Change-Id: I5924b7c6c9dfe61cb4089ad9a09d2da0c0bd18c4
diff --git a/tempest/api/identity/admin/v3/test_groups.py b/tempest/api/identity/admin/v3/test_groups.py
index 6e898b2..056f713 100644
--- a/tempest/api/identity/admin/v3/test_groups.py
+++ b/tempest/api/identity/admin/v3/test_groups.py
@@ -68,7 +68,7 @@
         # list users in group
         resp, group_users = self.client.list_group_users(group['id'])
         self.assertEqual(resp['status'], '200')
-        self.assertEqual(users.sort(), group_users.sort())
+        self.assertEqual(sorted(users), sorted(group_users))
         # delete user in group
         for user in users:
             resp, body = self.client.delete_group_user(group['id'],
@@ -77,6 +77,27 @@
         resp, group_users = self.client.list_group_users(group['id'])
         self.assertEqual(len(group_users), 0)
 
+    @test.attr(type='smoke')
+    def test_list_user_groups(self):
+        # create a user
+        resp, user = self.client.create_user(
+            data_utils.rand_name('User-'),
+            password=data_utils.rand_name('Pass-'))
+        self.addCleanup(self.client.delete_user, user['id'])
+        # create two groups, and add user into them
+        groups = []
+        for i in range(2):
+            name = data_utils.rand_name('Group-')
+            resp, group = self.client.create_group(name)
+            groups.append(group)
+            self.addCleanup(self.client.delete_group, group['id'])
+            self.client.add_group_user(group['id'], user['id'])
+        # list groups which user belongs to
+        resp, user_groups = self.client.list_user_groups(user['id'])
+        self.assertEqual('200', resp['status'])
+        self.assertEqual(sorted(groups), sorted(user_groups))
+        self.assertEqual(2, len(user_groups))
+
 
 class GroupsV3TestXML(GroupsV3TestJSON):
     _interface = 'xml'
diff --git a/tempest/services/identity/v3/json/identity_client.py b/tempest/services/identity/v3/json/identity_client.py
index 65f3355..285feb3 100644
--- a/tempest/services/identity/v3/json/identity_client.py
+++ b/tempest/services/identity/v3/json/identity_client.py
@@ -297,6 +297,12 @@
         body = json.loads(body)
         return resp, body['users']
 
+    def list_user_groups(self, user_id):
+        """Lists groups which a user belongs to."""
+        resp, body = self.get('users/%s/groups' % user_id)
+        body = json.loads(body)
+        return resp, body['groups']
+
     def delete_group_user(self, group_id, user_id):
         """Delete user in group."""
         resp, body = self.delete('groups/%s/users/%s' % (group_id, user_id))
diff --git a/tempest/services/identity/v3/xml/identity_client.py b/tempest/services/identity/v3/xml/identity_client.py
index 6ff6d56..d6c5bc1 100644
--- a/tempest/services/identity/v3/xml/identity_client.py
+++ b/tempest/services/identity/v3/xml/identity_client.py
@@ -52,6 +52,14 @@
                 array.append(common.xml_to_json(child))
         return array
 
+    def _parse_groups(self, node):
+        array = []
+        for child in node.getchildren():
+            tag_list = child.tag.split('}', 1)
+            if tag_list[1] == "group":
+                array.append(common.xml_to_json(child))
+        return array
+
     def _parse_group_users(self, node):
         array = []
         for child in node.getchildren():
@@ -342,6 +350,12 @@
         body = self._parse_group_users(etree.fromstring(body))
         return resp, body
 
+    def list_user_groups(self, user_id):
+        """Lists the groups which a user belongs to."""
+        resp, body = self.get('users/%s/groups' % user_id)
+        body = self._parse_groups(etree.fromstring(body))
+        return resp, body
+
     def delete_group_user(self, group_id, user_id):
         """Delete user in group."""
         resp, body = self.delete('groups/%s/users/%s' % (group_id, user_id))