docs: def server_version(self):
          """Attempts to determine the version of Vault that a
          server is running. Some actions will change on older
          Vault deployments."""
          health_url = "%s/v1/sys/health" % self.vault_addr
          resp = self.session.request('get', health_url, **self._kwargs)
          if resp.status_code == 200 or resp.status_code == 429:
              blob = resp.json()
              if 'version' in blob:
                  return blob['version']
          else:
              raise aomi.exceptions.VaultProblem('Health check failed')
  
          return None