code: def _guess_apiserver(apiserver_url=None):
      '''Try to guees the kubemaster url from environ,
      then from `/etc/kubernetes/config` file
      '''
      default_config = "/etc/kubernetes/config"
      if apiserver_url is not None:
          return apiserver_url
      if "KUBERNETES_MASTER" in os.environ:
          apiserver_url = os.environ.get("KUBERNETES_MASTER")
      elif __salt__['config.get']('k8s:master'):
          apiserver_url = __salt__['config.get']('k8s:master')
      elif os.path.exists(default_config) or __salt__['config.get']('k8s:config', ""):
          config = __salt__['config.get']('k8s:config', default_config)
          kubeapi_regex = re.compile(,
                                     re.MULTILINE)
          with salt.utils.files.fopen(config) as fh_k8s:
              for line in fh_k8s.readlines():
                  match_line = kubeapi_regex.match(line)
              if match_line:
                  apiserver_url = match_line.group(1)
      else:
          # we failed to discover, lets use k8s default address
          apiserver_url = "http://127.0.0.1:8080"
      log.debug("Discoverd k8s API server address: %s", apiserver_url)
      return apiserver_url
docs: Try to guees the kubemaster url from environ,
      then from `/etc/kubernetes/config` file