Stop leaking ceph df cmd in RBD utils

If the ceph df command fails in the get_pool_info
method of RBD utils the actual command executed
if seen by the users in the fault error message.

This hides the command behind a StorageError
exception and logs the exception instead of leaking
it to the users.

Change-Id: I6e3a73f2e04d1a7636daf96d5af73c9cf2fbe220
Closes-Bug: 1926978

nova/storage/rbd_utils.py

@@ -425,7 +425,14 @@ class RBDDriver(object):
         # MAX_AVAIL stat will divide by the replication size when doing the
         # calculation.
         args = ['ceph', 'df', '--format=json'] + self.ceph_args()
-        out, _ = processutils.execute(*args)
+
+        try:
+            out, _ = processutils.execute(*args)
+        except processutils.ProcessExecutionError:
+            LOG.exception('Could not determine disk usage')
+            raise exception.StorageError(
+                reason='Could not determine disk usage')
+
         stats = jsonutils.loads(out)
 
         # Find the pool for which we are configured.

nova/tests/unit/storage/test_rbd.py

@@ -13,6 +13,7 @@
 
 from eventlet import tpool
 import mock
+from oslo_concurrency import processutils
 from oslo_serialization import jsonutils
 from oslo_utils.fixture import uuidsentinel as uuids
 
@@ -653,6 +654,11 @@ class RbdTestCase(test.NoDBTestCase):
                     'used': ceph_df_json['pools'][1]['stats']['bytes_used']}
         self.assertDictEqual(expected, self.driver.get_pool_info())
 
+    @mock.patch('oslo_concurrency.processutils.execute', autospec=True,
+                side_effect=processutils.ProcessExecutionError("failed"))
+    def test_get_pool_info_execute_failed(self, mock_execute):
+        self.assertRaises(exception.StorageError, self.driver.get_pool_info)
+
     @mock.patch('oslo_concurrency.processutils.execute')
     def test_get_pool_info_not_found(self, mock_execute):
         # Make the pool something other than self.rbd_pool so it won't be found