Change get_credential to return generic Credential
A keyring backend may want to return SimpleCredential or
EnvironCredential
@@ -125,7 +125,7 @@ class KeyringBackend(metaclass=KeyringBackendMeta):
self,
service: str,
username: Optional[str],
- ) -> Optional[credentials.SimpleCredential]:
+ ) -> Optional[credentials.Credential]:
"""Gets the username and password for the service.
Returns a Credential instance.
