mypy: set no_implicit_optional

The current version of PEP-484 indicates that
type checkers should not allow implicit optional
parameters.

- https://www.python.org/dev/peps/pep-0484/#union-types
- python/mypy#9091

Change-Id: Ie3301798462a89af9fc0053070055a77a2437415

os_brick/initiator/connectors/base_rbd.py

@@ -15,7 +15,7 @@
 
 from __future__ import annotations
 
-from typing import Any
+from typing import Any, Optional  # noqa: H301
 
 from oslo_log import log as logging
 from oslo_utils import netutils
@@ -37,7 +37,7 @@ def _sanitize_host(host: str) -> str:
     @classmethod
     def _get_rbd_args(cls,
                       connection_properties: dict[str, Any],
-                      conf: str = None) -> list[str]:
+                      conf: Optional[str] = None) -> list[str]:
         user = connection_properties.get('auth_username')
         monitor_ips = connection_properties.get('hosts')
         monitor_ports = connection_properties.get('ports')

setup.cfg

@@ -48,3 +48,4 @@ warn_unused_ignores = true
 show_error_codes = true
 pretty = true
 html_report = mypy-report
+no_implicit_optional = true