code: def user_auth_token(self):
          
  
          # stage0 is a prequisite
          if not self.server_identity_is_verified:
              return False
  
          server_login_response = post_log_in(
              self,
              keyid=self.user_fingerprint
          )
  
          if not check_server_login_stage1_response(server_login_response):
              raise GPGAuthStage1Exception("Login endpoint wrongly formatted")
  
          # Get the encrypted User Auth Token
          encrypted_user_auth_token = unquote_plus(
              server_login_response.headers.get('X-GPGAuth-User-Auth-Token')
              .replace('\\\\', '\\')
          ).replace('\\ ', ' ')
  
          logger.debug('User token to decrypt: %s', encrypted_user_auth_token)
          logger.info('Decrypting the user authentication token; '
                      'password prompt expected')
  
          passphrase = None
          # For the sake of tests, allow one to set the passphrase onto
          # the object
          if hasattr(self, '_user_passphrase'):
              passphrase = self._user_passphrase
  
          user_auth_token = self.gpg.decrypt(encrypted_user_auth_token, always_trust=True, passphrase=passphrase)
  
          if not user_auth_token.ok:
              raise GPGAuthStage1Exception("Auth token decryption failed: %s", user_auth_token.status)
  
          logger.info('user_auth_token: %s', user_auth_token)
          return str(user_auth_token)
docs: GPGAuth Stage1