Adding tests on cache handler

New tests are:
- Permission denied
- File not found

Change-Id: I6d3343319ca6519fd9d215f2e8d3fa38516e9f4d

oslo_policy/tests/test_cache_handler.py

@@ -16,8 +16,10 @@
 """Test the cache handler module"""
 
 import os
+from unittest import mock
 
 import fixtures
+import oslo_config
 from oslotest import base as test_base
 
 from oslo_policy import _cache_handler as _ch
@@ -64,3 +66,29 @@ class CacheHandlerTest(test_base.BaseTestCase):
 
         reloaded, data = _ch.read_cached_file(file_cache, path)
         self.assertTrue(reloaded)
+
+    @mock.patch.object(_ch, 'LOG')
+    def test_reloading_cache_with_permission_denied(self, mock_log):
+        file_cache = {}
+
+        path = os.path.join(self.tmpdir.path, 'tmpfile')
+        with open(path, 'w+') as fp:
+            fp.write('test')
+
+        os.chmod(path, 000)
+        self.assertRaises(
+            oslo_config.cfg.ConfigFilesPermissionDeniedError,
+            _ch.read_cached_file, file_cache, path)
+        mock_log.error.assert_called_once()
+
+    @mock.patch.object(_ch, 'LOG')
+    def test_reloading_on_removed_file(self, mock_log):
+        file_cache = {}
+
+        # don't actually create the file
+        path = os.path.join(self.tmpdir.path, 'tmpfile')
+
+        reloaded, data = _ch.read_cached_file(file_cache, path)
+        self.assertEqual({}, data)
+        self.assertTrue(reloaded)
+        mock_log.error.assert_called_once()