Handle UncaughtPromiseRejection events

[heathkit]

If a webdriver command isn't properly awaited or promise chained and has an error, it'll throw an UncaughtPromiseRejection event. We should catch these events and log an error telling the user that they likely missed an await somewhere. Bonus points if we can get a stacktrace to the exact line that wasn't awaited.

[cnishina]

The unhandledPromiseRejection exists but I am unable to get to this condition.

[cnishina]

Actually was able to reproduce this in #5095 and have a better message set.

[cnishina]

describe('protractor with typescript typings', () => {
  it('sync works', () => {
    expect(1).toEqual(2);
    expect(3).toEqual(2);
  });

  it('async doesn\'t', async () => {
    expect(1).toEqual(2);
  });
});

config:

import {Config} from 'protractor';

export let config: Config = {
  framework: 'jasmine',
  capabilities: {
    browserName: 'chrome'
  },
  specs: [ 'spec.js' ],
  seleniumAddress: 'http://localhost:4444/wd/hub',
  onPrepare: () => {
    jasmine.getEnv().throwOnExpectationFailure(true);
  },
  // You could set no globals to true to avoid jQuery '$' and protractor '$'
  // collisions on the global namespace.
  noGlobals: true
};

Might be worth investigating before closing this issue.