lib/classes/CLI.js/CLI/generateCommandsHelp
class CLI:  generateCommandsHelp(commandsArray) {
    const commandName = commandsArray.join(' ');

    // Get all the commands using getCommands() with filtered entrypoint
    // commands and reduce to the required command.
    const allCommands = this.serverless.pluginManager.getCommands();
    const command = _.reduce(commandsArray, (currentCmd, cmd) => {
      if (currentCmd.commands && cmd in currentCmd.commands) {
        return currentCmd.commands[cmd];
      }
      return null;
    }, { commands: allCommands });

    // Throw error if command not found.
    if (!command) {
      const errorMessage = [
        `Serverless command "${commandName}" not found.`,
        ' Run "serverless help" for a list of all available commands.',
      ].join('');
      throw new this.serverless.classes.Error(errorMessage);
    }

    // print the name of the plugin
    this.consoleLog(chalk.yellow.underline(`Plugin: ${command.pluginName}`));

    this.displayCommandUsage(command, commandName);
    this.displayCommandOptions(command);

    this.consoleLog('');
  }