Include the service name in the error message when it's extends does not exist

Author: jan-matejka

podman_compose.py

@@ -1942,7 +1942,10 @@ def resolve_extends(
             normalize_service(from_service, subdirectory)
         else:
             from_service = services.get(from_service_name, {}).copy()
-            del from_service["_deps"]
+            try:
+                del from_service["_deps"]
+            except KeyError as e:
+                raise KeyError(f"{from_service_name} not found at services.{name}.extends definition")
             try:
                 del from_service["extends"]
             except KeyError: