Replace deprecated @abstractpoperty and ABCMeta-based ABC

src/linkahead/connection/authentication/interface.py

@@ -26,15 +26,13 @@ LinkAhead server.
 
 Implementing modules muts provide a `get_authentication_provider()` method.
 """
-from abc import ABCMeta, abstractmethod, abstractproperty
+from abc import ABC, abstractmethod
 import logging
 from ..utils import urlencode
 from ..interface import CaosDBServerConnection
 from ..utils import parse_auth_token, auth_token_to_cookie
 from ...exceptions import LoginFailedError
 
-# meta class compatible with Python 2 *and* 3:
-ABC = ABCMeta('ABC', (object, ), {'__slots__': ()})
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -262,10 +260,12 @@ class CredentialsProvider(ABC):
         None
         """
 
-    @abstractproperty
+    @property
+    @abstractmethod
     def password(self):
         """password."""
 
-    @abstractproperty
+    @property
+    @abstractmethod
     def username(self):
         """username."""