https://github.com/kohsuke/localizer/pull/11 actually works now.

cli/src/main/java/hudson/cli/CLI.java

@@ -809,9 +809,14 @@ public class CLI implements AutoCloseable {
         return authenticate(Collections.singleton(key));
     }
 
+    /** For access from {@code HelpCommand}. */
+    static String usage() {
+        return Messages.CLI_Usage();
+    }
+
     private static void printUsage(String msg) {
         if(msg!=null)   System.out.println(msg);
-        System.err.println(Messages.CLI_Usage());
+        System.err.println(usage());
     }
 
     static final Logger LOGGER = Logger.getLogger(CLI.class.getName());

core/src/main/java/hudson/cli/HelpCommand.java

@@ -53,7 +53,7 @@ public class HelpCommand extends CLICommand {
     protected int run() throws Exception {
         if (!Jenkins.getActiveInstance().hasPermission(Jenkins.READ)) {
             throw new AccessDeniedException("You must authenticate to access this Jenkins.\n"
-                    + hudson.cli.client.Messages.CLI_Usage());
+                    + CLI.usage());
         }
 
         if (command != null)