improve error message if users don't exist

pkgs/clan-cli/clan_cli/secrets/secrets.py

@@ -108,12 +108,23 @@ def groups_folder(group: str) -> Path:
     return sops_secrets_folder() / group / "groups"
 
 
+def list_directory(directory: Path) -> str:
+    if not directory.exists():
+        return "{directory} does not exist"
+    msg = f"\n{directory} contains:"
+    for f in directory.iterdir():
+        msg += f"\n  {f.name}"
+    return msg
+
+
 def allow_member(
     group_folder: Path, source_folder: Path, name: str, do_update_keys: bool = True
 ) -> None:
     source = source_folder / name
     if not source.exists():
-        raise ClanError(f"{name} does not exist in {source_folder}")
+        msg = f"{name} does not exist in {source_folder}"
+        msg += list_directory(source_folder)
+        raise ClanError(msg)
     group_folder.mkdir(parents=True, exist_ok=True)
     user_target = group_folder / name
     if user_target.exists():
@@ -134,7 +145,9 @@ def allow_member(
 def disallow_member(group_folder: Path, name: str) -> None:
     target = group_folder / name
     if not target.exists():
-        raise ClanError(f"{name} does not exist in group in {group_folder}")
+        msg = f"{name} does not exist in group in {group_folder}"
+        msg += list_directory(group_folder)
+        raise ClanError(msg)
 
     keys = collect_keys_for_path(group_folder.parent)