Unhandled promise rejection when shard takes too long to log in ("Client took too long to become ready")

[LakeYS]

This may be related to discord.js instead of the bot itself. Difficult to replicate.

(node:11632) UnhandledPromiseRejectionWarning: Error: Shard 0's Client took too
long to become ready.
    at Timeout.setTimeout [as _onTimeout] (C:\Content\_Dev\Discord-Trivia-Bot\no
de_modules\discord.js\src\sharding\Shard.js:89:31)
    at ontimeout (timers.js:482:11)
    at tryOnTimeout (timers.js:317:5)
    at Timer.listOnTimeout (timers.js:277:5)
    at emitWarning (internal/process/promises.js:65:17)
    at emitPendingUnhandledRejections (internal/process/promises.js:109:11)
    at runMicrotasksCallback (internal/process/next_tick.js:124:9)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)
(node:11632) Error: Shard 0's Client took too long to become ready.
    at Timeout.setTimeout [as _onTimeout] (C:\Content\_Dev\Discord-Trivia-Bot\node_modules\discord.js\src\sharding\Shard.js:89:31)
    at ontimeout (timers.js:482:11)
    at tryOnTimeout (timers.js:317:5)
    at Timer.listOnTimeout (timers.js:277:5)
(node:11632) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
    at emitWarning (internal/process/promises.js:92:15)
    at emitPendingUnhandledRejections (internal/process/promises.js:109:11)
    at runMicrotasksCallback (internal/process/next_tick.js:124:9)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

The shard does fix itself after a few seconds, so in most cases manual action is not required until unhandled promise rejections are entirely deprecated.

The code from discord.js for reference:

  spawn(args = this.manager.args, execArgv = this.manager.execArgv) {
    this.process = childProcess.fork(path.resolve(this.manager.file), args, {
      env: this.env, execArgv,
    })
      .on('exit', this._exitListener)
      .on('message', this._handleMessage.bind(this));

    /**
     * Emitted upon the creation of the shard's child process.
     * @event Shard#spawn
     * @param {ChildProcess} process Child process that was created
     */
    this.emit('spawn', this.process);

    return new Promise((resolve, reject) => {
      this.once('ready', resolve);
      this.once('disconnect', () => reject(new Error(`Shard ${this.id}'s Client disconnected before becoming ready.`)));
      this.once('death', () => reject(new Error(`Shard ${this.id}'s process exited before its Client became ready.`)));
      setTimeout(() => reject(new Error(`Shard ${this.id}'s Client took too long to become ready.`)), 30000);
    }).then(() => this.process);
  }

[LakeYS]

Confirmed still occurring as of Dec 7, 2018.

[LakeYS]

Stale