Deprecate --pull-source for container prepare command

The registry should be included in the --namespace argument to be
consistent with the other image references.

Change-Id: I0b0b8728b7752bdd4680a5a2bbf664f94f7d56d9
Closes-Bug: #1708303
Depends-On: I1769c7cf1c058328a8490228bdc4719e8d216ccb

releasenotes/notes/deprecate-pull-source-1d904126040c2eb1.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+- The command "openstack overcloud container image prepare" has deprecated
+  the --pull-source argument. The source registry should now be specified as
+  part of the --namespace argument.

tripleoclient/tests/v1/overcloud_image/test_container_image.py

@@ -92,7 +92,7 @@ class TestContainerImagePrepare(TestPluginV1):
             filter=mock.ANY,
             name_prefix='centos-binary-',
             name_suffix='',
-            namespace='tripleoupstream',
+            namespace='docker.io/tripleoupstream',
             tag='latest'
         )
 

tripleoclient/v1/container_image.py

@@ -177,8 +177,7 @@ class PrepareImageFiles(command.Command):
             dest="pull_source",
             metavar='<location>',
             help=_("Location of image registry to pull images from. "
-                   "If specified, a pull_source will be set for every image "
-                   "entry."),
+                   "(DEPRECATED. Include the registry in --namespace)"),
         )
         parser.add_argument(
             "--push-destination",
@@ -199,10 +198,10 @@ class PrepareImageFiles(command.Command):
         parser.add_argument(
             "--namespace",
             dest="namespace",
-            default="tripleoupstream",
+            default="docker.io/tripleoupstream",
             metavar='<namespace>',
             help=_("Override the default namespace substitution.\n"
-                   "Default: tripleoupstream"),
+                   "Default: docker.io/tripleoupstream"),
         )
         parser.add_argument(
             "--prefix",