Index: utils/update_test_checks.py
===================================================================
--- utils/update_test_checks.py
+++ utils/update_test_checks.py
@@ -74,6 +74,10 @@
   opt_basename = 'opt'
 
   test_paths = [test for pattern in args.tests for test in glob.glob(pattern)]
+  if not test_paths:
+    print('ERROR: No valid test paths', file=sys.stderr)
+    sys.exit(1)
+
   for test in test_paths:
     if args.verbose:
       print('Scanning for RUN lines in test file: %s' % (test,), file=sys.stderr)