new_contents: class RequireModule(object):
      """Decorator that raises import error if specified module isn't found."""
  
      def __init__(self, module_name):
          self.module_name = module_name
  
      def _require_module(self):
          try:
              __import__(self.module_name)
          except ImportError:
              raise ImportError(
                  '%s must be installed to use this helper.' % self.module_name)
  
      def __call__(self, func, *args, **kwargs):
          def wrapper(*args, **kwargs):
              self._require_module()
              return func(*args, **kwargs)
  
          return wrapper
  
subject: Add a RequireModule decorator for use by helpers