Deprecate group:os-apply-config with config-download

Instead of throwing an exception when a group:os-apply-config deployment
is found with config-download, just show a deprecation warning instead.
This will allow FFU to move forward without forcing users to update
older nic config templates that still use group:os-apply-config.

Change-Id: Icc803605b88d0655bfd45bdf1521298229a4722e
Closes-Bug: #1748976

releasenotes/notes/group-os-apply-config-warn-beece0b9fcff74b7.yaml

@@ -0,0 +1,4 @@
+---
+deprecations:
+  - group:os-apply-config deployments are deprecated for use with
+    config-download and they will not be applied.

tripleo_common/tests/utils/test_config.py

@@ -15,13 +15,13 @@ import fixtures
 import mock
 import os
 import uuid
+import warnings
 import yaml
 
 from mock import call
 from mock import patch
 
 from tripleo_common import constants
-from tripleo_common import exception
 from tripleo_common.tests import base
 from tripleo_common.tests.fake_config import fakes
 from tripleo_common.utils import config as ooo_config
@@ -345,5 +345,8 @@ class TestConfig(base.TestCase):
         mock_config_dict.side_effect = self._get_config_dict
 
         self.tmp_dir = self.useFixture(fixtures.TempDir()).path
-        self.assertRaises(exception.GroupOsApplyConfigException,
-                          self.config.download_config, stack, self.tmp_dir)
+        with warnings.catch_warnings(record=True) as w:
+            self.config.download_config(stack, self.tmp_dir)
+            self.assertEqual(1, len(w))
+            assert issubclass(w[-1].category, DeprecationWarning)
+            assert "group:os-apply-config is deprecated" in str(w[-1].message)

tripleo_common/utils/config.py

@@ -19,12 +19,15 @@ import re
 import shutil
 import six
 import tempfile
+import warnings
 import yaml
 
 import jinja2
 
 from tripleo_common import constants
-from tripleo_common import exception
+
+
+warnings.filterwarnings('once')
 
 
 class Config(object):
@@ -290,8 +293,10 @@ class Config(object):
                     d['scalar'] = True
 
                 if d['group'] == 'os-apply-config':
-                    raise exception.GroupOsApplyConfigException(
-                        d['deployment_name'])
+                    message = ("group:os-apply-config is deprecated. "
+                               "Deployment %s will not be applied by "
+                               "config-download." % d['deployment_name'])
+                    warnings.warn(message, DeprecationWarning)
 
             with open(group_var_server_path, 'w') as f:
                 f.write(group_var_server_template.render(