[placement] annotate loadapp as public interface

When Change-Id: I61d20c5d19797f7e66648c7864a632f3328be8ce was under
review there were questions about why the interface on deploy() was not
changed to remove the no-longer used project_name kwarg. I mistakenly
asserted that this was because it was a public interface for building
a Placement WSGI application. That's not the case. loadapp() is the
public interface.

This change annotates loadapp() as such, and removes the unused arg
deploy().

Change-Id: I9f3d03d964654ab1b9515ecd6fe35c518d5f496a
Related-Bug: #1734491

nova/api/openstack/placement/deploy.py

@@ -32,7 +32,7 @@ NAME = "nova"
 objects.register_all()
 
 
-def deploy(conf, project_name):
+def deploy(conf):
     """Assemble the middleware pipeline leading to the placement app."""
     if conf.api.auth_strategy == 'noauth2':
         auth_middleware = auth.NoAuthMiddleware
@@ -83,6 +83,20 @@ def deploy(conf, project_name):
     return application
 
 
+# NOTE(cdent): Althought project_name is no longer used because of the
+# resolution of https://bugs.launchpad.net/nova/+bug/1734491, loadapp()
+# is considered a public interface for the creation of a placement
+# WSGI app so must maintain its interface. The canonical placement WSGI
+# app is created by init_application in wsgi.py, but this is not
+# required and in fact can be limiting. loadapp() may be used from
+# fixtures or arbitrary WSGI frameworks and loaders.
 def loadapp(config, project_name=NAME):
-    application = deploy(config, project_name)
+    """WSGI application creator for placement.
+
+    :param config: An olso_config.cfg.ConfigOpts containing placement
+                   configuration.
+    :param project_name: oslo_config project name. Ignored, preserved for
+                         backwards compatibility
+    """
+    application = deploy(config)
     return application

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

@@ -34,7 +34,7 @@ class DeployTest(test.NoDBTestCase):
         self.flags(auth_uri=auth_uri, group='keystone_authtoken')
         # ensure that the auth_token middleware is chosen
         self.flags(auth_strategy='keystone', group='api')
-        app = deploy.deploy(CONF, 'nova')
+        app = deploy.deploy(CONF)
         req = webob.Request.blank('/resource_providers', method="GET")
 
         response = req.get_response(app)