docs: def find_critical(self, crit=True):
          """
          Return list of critical extensions (or list of non-cricital, if
          optional second argument is False
          """
          if crit:
              flag = 1
          else:
              flag = 0
          found = []
          end = len(self)
          index = -1
          while True:
              index = libcrypto.X509_get_ext_by_critical(self.cert.cert, flag,
                                                         index)
              if index >= end or index < 0:
                  break
              found.append(self[index])
          return found