docs: def check_command(args):
      """Checks that all dependencies in the specified requirements file are
      up to date."""
      outdated = check_requirements_file(args.requirements_file,
                                         args.skip_packages)
  
      if outdated:
          print('Requirements in {} are out of date:'.format(
              args.requirements_file))
  
          for item in outdated:
              print(' * {} is {} latest is {}.'.format(*item))
  
          sys.exit(1)
      else:
          print('Requirements in {} are up to date.'.format(
              args.requirements_file))