docs: def rulefiles(self, acc=None):
          """Return a list of rulefiles for the given account.
  
          Returns an empty list if none specified.
          """
          rulesdir = self.rulesdir(acc)
          rules = [os.path.join(rulesdir, x) for x in self.get('rules', acc, [])]
          if acc is not None:
              rules += self.rulefiles(acc=None)
          return rules