Bug 1786062 - Part 2: Fix pylint failure in vendor_rust.py CLOSED TREE

Differential Revision: https://phabricator.services.mozilla.com/D155474

python/mozbuild/mozbuild/vendor/vendor_rust.py

@@ -824,6 +824,11 @@ license file's hash.
                     {},
                     "Unknown vet error. Run `./mach cargo vet` for more information.",
                 )
+            failed = True
+
+        # If we failed when checking the crates list and/or running `cargo vet`,
+        # stop before invoking `cargo vendor`.
+        if failed:
             return False
 
         res = subprocess.run(