Raise error if /auth response is unexpected

Author: fqqb

yamcs-client/src/yamcs/client/core/__init__.py

@@ -17,6 +17,7 @@
 )
 
 from google.protobuf import timestamp_pb2
+from google.protobuf.message import DecodeError
 from yamcs.client.core.auth import APIKeyCredentials, Credentials
 from yamcs.client.core.context import Context
 from yamcs.client.core.exceptions import YamcsError
@@ -275,9 +276,14 @@ def get_auth_info(self) -> AuthInfo:
             headers={"Accept": "application/protobuf"},
         )
         if 200 <= response.status_code < 300:
-            message = auth_pb2.AuthInfo()
-            message.ParseFromString(response.content)
-            return AuthInfo(message)
+            try:
+                message = auth_pb2.AuthInfo()
+                message.ParseFromString(response.content)
+                return AuthInfo(message)
+            except DecodeError:
+                raise YamcsError(
+                    f"Unexpected response. Verify Yamcs URL: {self.ctx.url}"
+                )
         else:
             raise YamcsError(f"{response.status_code} Server Error")