conf: remove deprecated cells driver option

Change-Id: I582e53c24f1eebf83bbbdaa00164336d10bbcfdb
Implements: blueprint centralize-config-options-ocata

nova/cells/manager.py

@@ -22,12 +22,12 @@ import time
 from oslo_log import log as logging
 import oslo_messaging
 from oslo_service import periodic_task
-from oslo_utils import importutils
 from oslo_utils import timeutils
 import six
 from six.moves import range
 
 from nova.cells import messaging
+from nova.cells import rpc_driver as cells_rpc_driver
 from nova.cells import state as cells_state
 from nova.cells import utils as cells_utils
 import nova.conf
@@ -81,9 +81,7 @@ class CellsManager(manager.Manager):
             cell_state_manager = cells_state.CellStateManager
         self.state_manager = cell_state_manager()
         self.msg_runner = messaging.MessageRunner(self.state_manager)
-        cells_driver_cls = importutils.import_class(
+        self.driver = cells_rpc_driver.CellsRPCDriver()
-                CONF.cells.driver)
-        self.driver = cells_driver_cls()
         self.instances_to_heal = iter([])
 
     def post_start_hook(self):

nova/conf/cells.py

@@ -243,19 +243,6 @@ Possible values:
 ]
 
 cell_manager_opts = [
-    cfg.StrOpt('driver',
-        default='nova.cells.rpc_driver.CellsRPCDriver',
-        deprecated_for_removal=True,
-        deprecated_since="14.0.0",
-        deprecated_reason='The only available driver '
-                          'is the RPC driver.',
-        help="""Cells communication driver
-
-Driver for cell<->cell communication via RPC. This is used to
-setup the RPC consumers as well as to send a message to another cell.
-'nova.cells.rpc_driver.CellsRPCDriver' starts up 2 separate servers
-for handling inter-cell communication via RPC.
-"""),
     # TODO(sfinucan): Add min parameter
     cfg.IntOpt('instance_updated_at_threshold',
         default=3600,

nova/tests/unit/cells/fakes.py

@@ -168,8 +168,6 @@ def _build_cell_stub_infos(test_case):
 
 def init(test_case):
     global CELL_NAME_TO_STUB_INFO
-    test_case.flags(driver='nova.tests.unit.cells.fakes.FakeCellsDriver',
-            group='cells')
     CELL_NAME_TO_STUB_INFO = {}
     _build_cell_stub_infos(test_case)
 

releasenotes/notes/remove_deprecated_cells_driver_conf_opt-dbb80137b3632500.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    ``driver`` configuration option has been removed from ``cells``
+    group. There is only one possible driver for cells (CellsRPCDriver), which
+    makes this option redundant.