Fix a number of causes of unhandled rejections (and ensure tests fail when unhandled rejection occurs).

[stefanpenner]

prep work to address #9007

• fix all failures

[mike-north]

LGTM

[mike-north]

Seems like a good place to destructure, and I'm looking for a chance to make a multi-line suggestion

Suggested change

	let tmp = warning.line.split(':');
	let file = tmp[0].trim();
	let line = tmp[1];
	let [file, line] = warning.line.split(':').map(item => item.trim());

[stefanpenner]

Ya, that's a fine suggestion. But in general I try to avoid cosmetic cleanup in bug-fixes.

[mike-north]

I'm curious about whether there's there a reason you're not using Promise.resolve here?

Suggested change

	await new Promise(resolve => preexistingServer.close(resolve));
	await Promise.resolve(preexistingServer.close(resolve));

[stefanpenner]

We need a promise that fulfills only when the callback passed to prexistingServer.close is invoked.

Unfortunately the return value of preexistingServer.close is not meaningful when it comes to the above mentioned goal as preexistingServer.close(cb) === preexistingServer which when awaited fulfills on the next tick, regardless if the server has closed or not.

Two other reason to not take the alternative approach:

• await Promise.resolve(value) can be safely reduced to await value assuming Promise is the platform provided promise, which in this case it is. So if the return value of preexistingServer.close was meaningful, we would only need to await it.
• the resolve argument passed to close is not defined, and will trigger a thrown ReferenceError.