Add support for API message localization

Using the lazy gettext functionality from oslo gettextutils,
it is possible to use the Accept-Language header to translate
an exception message to the user requested locale and return
that translation from the API.

Implements bp user-locale-api

Change-Id: I446fdf4b9843155e0c818c271114b1e2e4f43b64

nova/test.py

@@ -27,6 +27,7 @@ import eventlet
 eventlet.monkey_patch(os=False)
 
 import copy
+import gettext
 import os
 import shutil
 import sys
@@ -191,6 +192,17 @@ class MoxStubout(fixtures.Fixture):
         self.addCleanup(self.mox.VerifyAll)
 
 
+class TranslationFixture(fixtures.Fixture):
+    """Use gettext NullTranslation objects in tests."""
+
+    def setUp(self):
+        super(TranslationFixture, self).setUp()
+        nulltrans = gettext.NullTranslations()
+        gettext_fixture = fixtures.MonkeyPatch('gettext.translation',
+                                               lambda *x, **y: nulltrans)
+        self.gettext_patcher = self.useFixture(gettext_fixture)
+
+
 class TestingException(Exception):
     pass
 
@@ -216,6 +228,7 @@ class TestCase(testtools.TestCase):
             self.useFixture(fixtures.Timeout(test_timeout, gentle=True))
         self.useFixture(fixtures.NestedTempfile())
         self.useFixture(fixtures.TempHomeDir())
+        self.useFixture(TranslationFixture())
 
         if (os.environ.get('OS_STDOUT_CAPTURE') == 'True' or
                 os.environ.get('OS_STDOUT_CAPTURE') == '1'):

nova/utils.py

@@ -43,6 +43,7 @@ from oslo.config import cfg
 
 from nova import exception
 from nova.openstack.common import excutils
+from nova.openstack.common import gettextutils
 from nova.openstack.common.gettextutils import _
 from nova.openstack.common import importutils
 from nova.openstack.common import lockutils
@@ -476,6 +477,8 @@ def utf8(value):
     """
     if isinstance(value, unicode):
         return value.encode('utf-8')
+    elif isinstance(value, gettextutils.Message):
+        return unicode(value).encode('utf-8')
     assert isinstance(value, str)
     return value