[placement] Allow both /placement and /placement/ to work

When mounted under a prefix (such as /placement) the service was
only returning the home document at /placement/ not /placement. In
the context of having a prefix, we'd generally like the latter to
work and for '/' to work when there is no prefix. This allows both.

Note that this doesn't make /placement/resource_providers/ work, and
we don't want that.

Change-Id: I0ac92bf9982227d5f4915175182e5230aeb039b4
Closes-Bug: #1626490

nova/api/openstack/placement/handler.py

@@ -48,6 +48,14 @@ ROUTE_DECLARATIONS = {
     '/': {
         'GET': root.home,
     },
+    # NOTE(cdent): This allows '/placement/' and '/placement' to
+    # both work as the root of the service, which we probably want
+    # for those situations where the service is mounted under a
+    # prefix (as it is in devstack). While weird, an empty string is
+    # a legit key in a dictionary and matches as desired in Routes.
+    '': {
+        'GET': root.home,
+    },
     '/resource_providers': {
         'GET': resource_provider.list_resource_providers,
         'POST': resource_provider.create_resource_provider

nova/tests/unit/api/openstack/placement/test_handler.py

@@ -18,6 +18,7 @@ import routes
 import webob
 
 from nova.api.openstack.placement import handler
+from nova.api.openstack.placement.handlers import root
 from nova import test
 from nova.tests import uuidsentinel
 
@@ -112,3 +113,20 @@ class PlacementLoggingTest(test.NoDBTestCase):
                           app, environ, start_response)
         mocked_log.error.assert_not_called()
         mocked_log.exception.assert_not_called()
+
+
+class DeclarationsTest(test.NoDBTestCase):
+
+    def setUp(self):
+        super(DeclarationsTest, self).setUp()
+        self.mapper = handler.make_map(handler.ROUTE_DECLARATIONS)
+
+    def test_root_slash_match(self):
+        environ = _environ(path='/')
+        result = self.mapper.match(environ=environ)
+        self.assertEqual(root.home, result['action'])
+
+    def test_root_empty_match(self):
+        environ = _environ(path='')
+        result = self.mapper.match(environ=environ)
+        self.assertEqual(root.home, result['action'])