Implements import_group

Created import_group method in cfg.py
Added testcases

Fixes bug #1107843

Change-Id: I427d4069dacbb6e586687370adbb08b5d50f7b63

oslo/config/cfg.py

@@ -1297,6 +1297,24 @@ class ConfigOpts(collections.Mapping):
         __import__(module_str)
         self._get_opt_info(name, group)
 
+    def import_group(self, group, module_str):
+        """Import an option group from a module.
+
+        Import a module and check that a given option group is registered.
+
+        This is intended for use with global configuration objects
+        like cfg.CONF where modules commonly register options with
+        CONF at module load time. If one module requires an option group
+        defined by another module it can use this method to explicitly
+        declare the dependency.
+
+        :param group: an option OptGroup object or group name
+        :param module_str: the name of a module to import
+        :raises: ImportError, NoSuchGroupError
+        """
+        __import__(module_str)
+        self._get_group(group)
+
     @__clear_cache
     def set_override(self, name, override, group=None):
         """Override an opt value.

tests/test_cfg.py

@@ -1241,6 +1241,23 @@ class ImportOptTestCase(BaseTestCase):
                           'blaa', 'tests.testmods.blaa_opt', group='blaa')
 
 
+class ImportGroupTestCase(BaseTestCase):
+
+    def test_import_group(self):
+        self.assertFalse(hasattr(CONF, 'qux'))
+        CONF.import_group('qux', 'tests.testmods.baz_qux_opt')
+        self.assertTrue(hasattr(CONF, 'qux'))
+        self.assertTrue(hasattr(CONF.qux, 'baz'))
+
+    def test_import_group_import_error(self):
+        self.assertRaises(ImportError, CONF.import_group,
+                          'qux', 'tests.testmods.bazzz_quxxx_opt')
+
+    def test_import_group_no_such_group(self):
+        self.assertRaises(NoSuchGroupError, CONF.import_group,
+                          'quxxx', 'tests.testmods.baz_qux_opt')
+
+
 class RequiredOptsTestCase(BaseTestCase):
 
     def setUp(self):

tests/testmods/baz_qux_opt.py

@@ -0,0 +1,21 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2013 Intel Corporation.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from oslo.config import cfg
+
+CONF = cfg.CONF
+
+CONF.register_opt(cfg.StrOpt('baz'), group='qux')