diff --git a/glance_store/exceptions.py b/glance_store/exceptions.py
index 79af2987..ef4a363d 100644
--- a/glance_store/exceptions.py
+++ b/glance_store/exceptions.py
@@ -15,7 +15,8 @@
 
 """Glance Store exception subclasses"""
 
-from six.moves import urllib
+import six
+import six.moves.urllib.parse as urlparse
 
 from glance_store import i18n
 
@@ -32,7 +33,7 @@ class UnsupportedBackend(BackendException):
 
 class RedirectException(Exception):
     def __init__(self, url):
-        self.url = urllib.parse.urlparse(url)
+        self.url = urlparse.urlparse(url)
 
 
 class GlanceStoreException(Exception):
@@ -43,11 +44,24 @@ class GlanceStoreException(Exception):
     a 'message' property. That message will get printf'd
     with the keyword arguments provided to the constructor.
     """
-    message = ''
+    message = _("An unknown exception occurred")
 
-    def __init__(self, **kwargs):
-        self.msg = kwargs.pop('message', None) or self.message % kwargs
-        super(Exception, self).__init__(self.msg)
+    def __init__(self, message=None, **kwargs):
+        if not message:
+            message = self.message
+        try:
+            if kwargs:
+                message = message % kwargs
+        except Exception:
+                pass
+        self.msg = message
+        super(GlanceStoreException, self).__init__(message)
+
+    def __unicode__(self):
+        # NOTE(flwang): By default, self.msg is an instance of Message, which
+        # can't be converted by str(). Based on the definition of
+        # __unicode__, it should return unicode always.
+        return six.text_type(self.msg)
 
 
 class MissingCredentialError(GlanceStoreException):
diff --git a/glance_store/tests/unit/test_exceptions.py b/glance_store/tests/unit/test_exceptions.py
new file mode 100644
index 00000000..d9fe1e18
--- /dev/null
+++ b/glance_store/tests/unit/test_exceptions.py
@@ -0,0 +1,57 @@
+# Copyright 2015 OpenStack Foundation
+# All Rights Reserved.
+#
+#    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_utils import encodeutils
+from oslotest import base
+import six
+
+import glance_store
+
+
+class TestExceptions(base.BaseTestCase):
+    """Test routines in glance_store.common.utils."""
+    def test_backend_exception(self):
+        msg = glance_store.BackendException()
+        self.assertIn(u'', encodeutils.exception_to_unicode(msg))
+
+    def test_unsupported_backend_exception(self):
+        msg = glance_store.UnsupportedBackend()
+        self.assertIn(u'', encodeutils.exception_to_unicode(msg))
+
+    def test_redirect_exception(self):
+        # Just checks imports work ok
+        glance_store.RedirectException(url='http://localhost')
+
+    def test_exception_no_message(self):
+        msg = glance_store.NotFound()
+        self.assertIn('Image %(image)s not found',
+                      encodeutils.exception_to_unicode(msg))
+
+    def test_exception_not_found_with_image(self):
+        msg = glance_store.NotFound(image='123')
+        self.assertIn('Image 123 not found',
+                      encodeutils.exception_to_unicode(msg))
+
+    def test_exception_with_message(self):
+        msg = glance_store.NotFound('Some message')
+        self.assertIn('Some message', encodeutils.exception_to_unicode(msg))
+
+    def test_exception_with_kwargs(self):
+        msg = glance_store.NotFound('Message: %(foo)s', foo='bar')
+        self.assertIn('Message: bar', encodeutils.exception_to_unicode(msg))
+
+    def test_non_unicode_error_msg(self):
+        exc = glance_store.NotFound(str('test'))
+        self.assertIsInstance(encodeutils.exception_to_unicode(exc),
+                              six.text_type)