Fix get_location for opts in groups

get_location defines the type of its ``group`` parameter as a str,
but it then passes that directly into _do_get, which expects an
OptGroup for its parameter. When it tries to reference group.name
it blows up because a str doesn't have a .name attr.

In the interest of not changing either API, this change coerces the
group str into an OptGroup.

Closes-Bug: 1807230
Change-Id: Iae547cbd63059fa19691a7f7fe398b148effd177

oslo_config/cfg.py

@@ -3095,7 +3095,8 @@ class ConfigOpts(collections.Mapping):
 
         .. versionadded:: 5.3.0
         """
-        value, loc = self._do_get(name, group, None)
+        opt_group = OptGroup(group) if group is not None else None
+        value, loc = self._do_get(name, opt_group, None)
         return loc
 
     class GroupAttr(collections.Mapping):

oslo_config/tests/test_get_location.py

@@ -68,6 +68,11 @@ class GetLocationTestCase(base.BaseTestCase):
             default='cli_opt_default',
         )
         self.conf.register_cli_opt(self.cli_opt)
+        self.group_opt = cfg.StrOpt(
+            'group_opt',
+            default='group_opt_default',
+        )
+        self.conf.register_opt(self.group_opt, group='group')
 
     def test_opt_default(self):
         self.conf([])
@@ -189,3 +194,12 @@ class GetLocationTestCase(base.BaseTestCase):
         # We expect register_opt() to return False to indicate that
         # the option was already registered.
         self.assertFalse(self.conf.register_opt(dupe_opt))
+
+    def test_group_opt(self):
+        self.conf([])
+        loc = self.conf.get_location('group_opt', 'group')
+        self.assertEqual(
+            cfg.Locations.opt_default,
+            loc.location,
+        )
+        self.assertIn('test_get_location.py', loc.detail)