fix(ratchet): refuse a package directory that does not exist

napalm-hpe-aruba-procurve ships napalm_procurve; guessed from its name, the
ratchet measured nothing and wrote an empty baseline without a word.

napalm_standard/cli.py

@@ -40,7 +40,11 @@ def _check(args: argparse.Namespace) -> int:
 
 
 def _ratchet(args: argparse.Namespace) -> int:
-    code, text = ratchet.run(args.path, _repo(args.path).package, write=args.write)
+    try:
+        code, text = ratchet.run(args.path, _repo(args.path).package, write=args.write)
+    except FileNotFoundError as exc:
+        print(exc, file=sys.stderr)
+        return 2
     print(text)
     return code