makeUpgradeDisconnection = (upgradeMessage, toIncarnationNumber) =>
  harden({
    name: 'vatUpgraded',
    upgradeMessage,
    incarnationNumber: toIncarnationNumber,
  })
Copied from
https://github.com/Agoric/agoric-sdk/blob/286302a192b9eb2e222faa08479f496645bb7b9a/packages/internal/src/upgrade-api.js#L25-L39
to verify that an UpgradeDisconnection object is throwable, as we need it
to be.

Makes an Error-like object for use as the rejection reason of promises
abandoned by upgrade.

@param {string} upgradeMessage
@param {number} toIncarnationNumber
@returns {UpgradeDisconnection}