Try decoding string to UTF-8 on error message fail

Database Errors from SQLAlchemy tend to get mangled into ASCII. If an
error is process that contains UTF-8 data in ASCII form if fails to
build the message and will lead to a 5xx error. Catch the error and try
to decode it to create the message again, if that doesn't work at least
fail gracefully.

Closes-Bug: 1253905
Change-Id: Iecb1170387c51064918780dc6de07db7ca8aeeee
(cherry picked from commit dcefe5874d)

keystone/exception.py

@@ -14,8 +14,11 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import six
+
 from keystone.common import config
 from keystone.openstack.common import log as logging
+from keystone.openstack.common import strutils
 
 
 CONF = config.CONF
@@ -56,7 +59,20 @@ class Error(StandardError):
 
         """
         if not message:
-            message = self.message_format % kwargs
+            try:
+                message = self.message_format % kwargs
+            except UnicodeDecodeError:
+                try:
+                    kwargs = dict([(k, strutils.safe_decode(v)) for k, v in
+                                   six.iteritems(kwargs)])
+                except UnicodeDecodeError:
+                    # NOTE(jamielennox): This is the complete failure case
+                    # at least by showing the template we have some idea
+                    # of where the error is coming from
+                    message = self.message_format
+                else:
+                    message = self.message_format % kwargs
+
         return message
 
 

keystone/tests/test_exception.py

@@ -85,6 +85,20 @@ class ExceptionTestCase(tests.TestCase):
         except UnicodeEncodeError:
             self.fail("unicode error message not supported")
 
+    def test_unicode_string(self):
+        e = exception.ValidationError(attribute='xx',
+                                      target='Long \xe2\x80\x93 Dash')
+
+        self.assertIn(u'\u2013', e.message)
+
+    def test_invalid_unicode_string(self):
+        # NOTE(jamielennox): This is a complete failure case so what is
+        # returned in the e.message is not that important so long as there is
+        # an error with a message
+        e = exception.ValidationError(attribute='xx',
+                                      target='\xe7a va')
+        self.assertIn('%(attribute)', e.message)
+
 
 class SecurityErrorTestCase(ExceptionTestCase):
     """Tests whether security-related info is exposed to the API user."""