Drop usage of pkg_resources

The pkg_resources module was deprecated. It was removed from the core
Python and has been moved to setuptools in Python 3.12.

Replace usage of pkg_resources.declare_namespace by implicit namespace
package[1][2] which has been supported since Python 3.3.

[1] https://peps.python.org/pep-0420/
[2] https://packaging.python.org/en/latest/guides/packaging-namespace-packages/

Closes-Bug: #2083620
Change-Id: If1a9d7048412b60bfa997028fb3df5773e66693c

nova/tests/unit/api/test_wsgi.py

@@ -19,7 +19,9 @@
 Test WSGI basics and provide some helper functions for other WSGI tests.
 """
 
+import collections
 import tempfile
+from unittest import mock
 
 import routes
 import webob
@@ -29,6 +31,11 @@ import nova.exception
 from nova import test
 
 
+os_uname = collections.namedtuple(
+    'uname_result', ['sysname', 'nodename', 'release', 'version', 'machine'],
+)
+
+
 class TestRouter(test.NoDBTestCase):
 
     def test_router(self):
@@ -104,7 +111,10 @@ document_root = /tmp
         )
 
     def test_app_found(self):
-        url_parser = self.loader.load_app("test_app")
+        with mock.patch('os.uname') as mock_uname:
+            mock_uname.return_value = os_uname(
+                'Linux', '', '5.10.13-200-generic', '', 'x86_64')
+            url_parser = self.loader.load_app("test_app")
         self.assertEqual("/tmp", url_parser.directory)
 
     def tearDown(self):

nova/virt/__init__.py

@@ -1,18 +0,0 @@
-# Copyright 2016 IBM Corp.
-#
-# All Rights Reserved.
-#
-#    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.
-
-# Allow composition of nova.virt namespace from disparate packages.
-__import__('pkg_resources').declare_namespace(__name__)