Fix the error about the translation of KarborException message

1, Introduce FaultWrapper from cinder to make exceptions into karbor's
wsgi faults. So that the messages can be translated, it can be shown
in a WSGI response.

2, Avoid Forcing the Translation of Translatable Variables[1]

[1]http://docs.openstack.org/developer/oslo.i18n/guidelines.html#avoid-forcing-the-translation-of-translatable-variables

Closes-Bug: 1698757
Change-Id: Id85871b3a4c9ec7049f42e15141a678dba7316c2

etc/api-paste.ini

@@ -9,12 +9,15 @@ use = egg:Paste#urlmap
 
 [composite:openstack_karbor_api_v1]
 use = call:karbor.api.middleware.auth:pipeline_factory
-noauth = request_id catch_errors noauth apiv1
-keystone = request_id catch_errors authtoken keystonecontext apiv1
+noauth = request_id faultwrap noauth apiv1
+keystone = request_id faultwrap authtoken keystonecontext apiv1
 
 [filter:request_id]
 paste.filter_factory = oslo_middleware:RequestId.factory
 
+[filter:faultwrap]
+paste.filter_factory = karbor.api.middleware.fault:FaultWrapper.factory
+
 [filter:catch_errors]
 paste.filter_factory = oslo_middleware:CatchErrors.factory
 

karbor/api/middleware/fault.py

@@ -0,0 +1,65 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from oslo_log import log as logging
+import six
+from six.moves import http_client
+import webob.dec
+import webob.exc
+
+from karbor.api.openstack import wsgi
+from karbor import exception
+from karbor import utils
+from karbor.wsgi import common as base_wsgi
+
+
+LOG = logging.getLogger(__name__)
+
+
+class FaultWrapper(base_wsgi.Middleware):
+    """Calls down the middleware stack, making exceptions into faults."""
+
+    _status_to_type = {}
+
+    @staticmethod
+    def status_to_type(status):
+        if not FaultWrapper._status_to_type:
+            for clazz in utils.walk_class_hierarchy(webob.exc.HTTPError):
+                FaultWrapper._status_to_type[clazz.code] = clazz
+        return FaultWrapper._status_to_type.get(
+            status, webob.exc.HTTPInternalServerError)()
+
+    def _error(self, inner, req):
+        safe = getattr(inner, 'safe', False)
+        headers = getattr(inner, 'headers', None)
+        status = getattr(inner, 'code', http_client.INTERNAL_SERVER_ERROR)
+        if status is None:
+            status = http_client.INTERNAL_SERVER_ERROR
+
+        msg_dict = dict(url=req.url, status=status)
+        LOG.info("%(url)s returned with HTTP %(status)d", msg_dict)
+        outer = self.status_to_type(status)
+        if headers:
+            outer.headers = headers
+
+        if safe:
+            msg = (inner.msg if isinstance(inner, exception.KarborException)
+                   else six.text_type(inner))
+            outer.explanation = msg
+        return wsgi.Fault(outer)
+
+    @webob.dec.wsgify(RequestClass=wsgi.Request)
+    def __call__(self, req):
+        try:
+            return req.get_response(self.application)
+        except Exception as ex:
+            return self._error(ex, req)

karbor/exception.py

@@ -83,7 +83,7 @@ class KarborException(Exception):
     message = _("An unknown exception occurred.")
     code = http_client.INTERNAL_SERVER_ERROR
     headers = {}
-    safe = False
+    safe = True
 
     def __init__(self, message=None, **kwargs):
         """Initiate the instance of KarborException
@@ -132,7 +132,7 @@ class KarborException(Exception):
         super(KarborException, self).__init__(message)
 
     def __unicode__(self):
-        return six.text_type(self.msg)
+        return self.msg
 
 
 class NotAuthorized(KarborException):

karbor/tests/unit/test_utils.py

@@ -0,0 +1,42 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from karbor.tests import base
+
+from karbor import utils
+
+
+class WalkClassHierarchyTestCase(base.TestCase):
+    def test_walk_class_hierarchy(self):
+        class A(object):
+            pass
+
+        class B(A):
+            pass
+
+        class C(A):
+            pass
+
+        class D(B):
+            pass
+
+        class E(A):
+            pass
+
+        class_pairs = zip((D, B, E),
+                          utils.walk_class_hierarchy(A, encountered=[C]))
+        for actual, expected in class_pairs:
+            self.assertEqual(expected, actual)
+
+        class_pairs = zip((D, B, C, E), utils.walk_class_hierarchy(A))
+        for actual, expected in class_pairs:
+            self.assertEqual(expected, actual)

karbor/utils.py

@@ -162,3 +162,16 @@ def validate_integer(value, name, min_value=None, max_value=None):
                          {'value_name': name, 'max_value': max_value}))
 
     return value
+
+
+def walk_class_hierarchy(clazz, encountered=None):
+    """Walk class hierarchy, yielding most derived classes first."""
+    if not encountered:
+        encountered = []
+    for subclass in clazz.__subclasses__():
+        if subclass not in encountered:
+            encountered.append(subclass)
+            # drill down to leaves first
+            for subsubclass in walk_class_hierarchy(subclass, encountered):
+                yield subsubclass
+            yield subclass