docs: def _extcap_call(prog, args, keyword, values):
      """Function used to call a program using the extcap format,
      then parse the results"""
      p = subprocess.Popen(
          [prog] + args,
          stdout=subprocess.PIPE, stderr=subprocess.PIPE
      )
      data, err = p.communicate()
      if p.returncode != 0:
          raise OSError("%s returned with error code %s: %s" % (prog,
                                                                p.returncode,
                                                                err))
      data = plain_str(data)
      res = []
      for ifa in data.split("\n"):
          ifa = ifa.strip()
          if not ifa.startswith(keyword):
              continue
          res.append(tuple([re.search(r"{%s=([^}]*)}" % val, ifa).group(1)
                     for val in values]))
      return res