Remove import of 'imp' module

Use importlib.util module instead of imp, since it's
being deprecated:

  DeprecationWarning: the imp module is deprecated in favour of
  importlib; see the module's documentation for alternative uses

Had to change test setup to call super() first to get around a
config issue I was seeing locally, causing the entire class of
tests to fail:

  oslo_config.cfg.NoSuchOptError: no such option api_extensions_path
  in group [DEFAULT]

Closes-bug: #1981077

Change-Id: Ic171028a661c3f9f83f6758a57aaeab4450aa907

neutron/api/extensions.py

@@ -14,7 +14,7 @@
 #    under the License.
 
 import collections
-import imp
+from importlib import util as imp_util
 import os
 
 from keystoneauth1 import loading as ks_loading
@@ -451,7 +451,9 @@ class ExtensionManager(object):
                 mod_name, file_ext = os.path.splitext(os.path.split(f)[-1])
                 ext_path = os.path.join(path, f)
                 if file_ext.lower() == '.py' and not mod_name.startswith('_'):
-                    mod = imp.load_source(mod_name, ext_path)
+                    spec = imp_util.spec_from_file_location(mod_name, ext_path)
+                    mod = imp_util.module_from_spec(spec)
+                    spec.loader.exec_module(mod)
                     ext_name = mod_name.capitalize()
                     new_ext_class = getattr(mod, ext_name, None)
                     if not new_ext_class:

neutron/tests/unit/api/test_extensions.py

@@ -102,8 +102,8 @@ class FakePluginWithExtension(service_base.ServicePluginBase):
 class ExtensionPathTest(base.BaseTestCase):
 
     def setUp(self):
-        self.base_path = extensions.get_extensions_path()
         super(ExtensionPathTest, self).setUp()
+        self.base_path = extensions.get_extensions_path()
 
     def test_get_extensions_path_with_plugins(self):
         cfg.CONF.set_override('api_extensions_path',

neutron/tests/unit/db/test_ovn_revision_numbers_db.py

@@ -134,6 +134,21 @@ class TestMaintenancePlugin(test_securitygroup.SecurityGroupTestPlugin,
                                    sgag_def.ALIAS]
 
 
+# Needed to extend resources for revision number tests, this is the
+# least invasive way
+class TestExtensionManager(extensions.PluginAwareExtensionManager):
+
+    def get_resources(self):
+        resources = super(TestExtensionManager, self).get_resources()
+        sg_ext_mgr = test_securitygroup.SecurityGroupTestExtensionManager
+        sg_resources = sg_ext_mgr.get_resources(self)
+        sg_resources_collection_names = [
+            res.collection for res in sg_resources]
+        resources = [r for r in resources
+                     if r.collection not in sg_resources_collection_names]
+        return resources + sg_resources
+
+
 class TestRevisionNumberMaintenance(test_securitygroup.SecurityGroupsTestCase,
                                     test_l3.L3NatTestCaseMixin):
 
@@ -141,13 +156,13 @@ class TestRevisionNumberMaintenance(test_securitygroup.SecurityGroupsTestCase,
         service_plugins = {
             'router':
             'neutron.tests.unit.extensions.test_l3.TestL3NatServicePlugin'}
+        super(TestRevisionNumberMaintenance, self).setUp(
+              plugin=PLUGIN_CLASS, service_plugins=service_plugins)
         l3_plugin = test_l3.TestL3NatServicePlugin()
         sec_plugin = test_securitygroup.SecurityGroupTestPlugin()
-        ext_mgr = extensions.PluginAwareExtensionManager(
+        ext_mgr = TestExtensionManager(
             EXTENSIONS_PATH, {'router': l3_plugin, 'sec': sec_plugin}
         )
-        super(TestRevisionNumberMaintenance, self).setUp(
-            plugin=PLUGIN_CLASS, service_plugins=service_plugins)
         app = config.load_paste_app('extensions_test_app')
         self.ext_api = extensions.ExtensionMiddleware(app, ext_mgr=ext_mgr)
         self.session = db_api.get_writer_session()