Handle API NotFound exceptions at WSGI level

Throughout the API code we keep catching NotFound exceptions in their
various forms and converting them to webob.exc.HTTPNotFound exceptions,
but we can leave the WSGI fault handler convert them on its own.

This patch changes current behavior and removes the exception handling
closer to the operation so that those exceptions can be handled at the
WSGI level.

This has the following benefits:

- Reduces code complexity
- Increases code readability
- Provides consistent error responses, as messages are stored on the
  Exceptions.
- Prevents raising errors with only partial information (we have cases
  now that were removing the UUID from the message because they used a
  custom message).  For example: before returned error would be "The
  resource could not be found", and now we raise "Volume type encryption
  for type 4e9e6d23-eed0-426d-b90a-28f87a94b6fe does not exist."
  automatically.
- Reduces workload for the translation team because we remove all
  unnecessary custom messages.

Change-Id: I09f98921fdc2400cc3f6056e59001100abe06920

cinder/quota_utils.py

@@ -12,8 +12,6 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
-import webob
-
 from oslo_config import cfg
 from oslo_log import log as logging
 
@@ -101,30 +99,26 @@ def get_project_hierarchy(context, project_id, subtree_as_ids=False,
     If the domain is being used as the top most parent, it is filtered out from
     the parent tree and parent_id.
     """
-    try:
-        keystone = _keystone_client(context)
-        generic_project = GenericProjectInfo(project_id, keystone.version)
-        if keystone.version == 'v3':
-            project = keystone.projects.get(project_id,
-                                            subtree_as_ids=subtree_as_ids,
-                                            parents_as_ids=parents_as_ids)
+    keystone = _keystone_client(context)
+    generic_project = GenericProjectInfo(project_id, keystone.version)
+    if keystone.version == 'v3':
+        project = keystone.projects.get(project_id,
+                                        subtree_as_ids=subtree_as_ids,
+                                        parents_as_ids=parents_as_ids)
 
-            generic_project.parent_id = None
-            if project.parent_id != project.domain_id:
-                generic_project.parent_id = project.parent_id
+        generic_project.parent_id = None
+        if project.parent_id != project.domain_id:
+            generic_project.parent_id = project.parent_id
 
-            generic_project.subtree = (
-                project.subtree if subtree_as_ids else None)
+        generic_project.subtree = (
+            project.subtree if subtree_as_ids else None)
 
-            generic_project.parents = None
-            if parents_as_ids:
-                generic_project.parents = _filter_domain_id_from_parents(
-                    project.domain_id, project.parents)
+        generic_project.parents = None
+        if parents_as_ids:
+            generic_project.parents = _filter_domain_id_from_parents(
+                project.domain_id, project.parents)
 
-            generic_project.is_admin_project = is_admin_project
-    except exceptions.NotFound:
-        msg = (_("Tenant ID: %s does not exist.") % project_id)
-        raise webob.exc.HTTPNotFound(explanation=msg)
+        generic_project.is_admin_project = is_admin_project
 
     return generic_project