made AuthClient ABC for early error message

scilog/authclient.py

@@ -1,4 +1,5 @@
 import getpass
+from abc import ABC, abstractmethod
 from .config import Config
 from .utils import typename
 
@@ -9,7 +10,7 @@ AUTH_HEADERS = {
 }
 
 
-class AuthClient:
+class AuthClient(ABC):
 
     def __init__(self, address):
         self.address = address.rstrip("/")
@@ -22,6 +23,10 @@ class AuthClient:
         return f"{tn} @ {self.address}"
 
 
+    @abstractmethod
+    def authenticate(self, username, password):
+        raise NotImplementedError
+
     @property
     def auth_headers(self):
         headers = AUTH_HEADERS.copy()