types: CredentialsConfiguration.conf can return None

certbot-dns-sakuracloud/certbot_dns_sakuracloud/_internal/dns_sakuracloud.py

@@ -2,6 +2,7 @@
 import logging
 from typing import Any
 from typing import Callable
+from typing import cast
 from typing import Optional
 
 from lexicon.providers import sakuracloud
@@ -64,8 +65,8 @@ class Authenticator(dns_common.DNSAuthenticator):
         if not self.credentials:  # pragma: no cover
             raise errors.Error("Plugin has not been prepared.")
         return _SakuraCloudLexiconClient(
-            self.credentials.conf('api-token'),
-            self.credentials.conf('api-secret'),
+            cast(str, self.credentials.conf('api-token')),
+            cast(str, self.credentials.conf('api-secret')),
             self.ttl
         )