Add messages for rejected promises

extensions/github-authentication/src/common/utils.ts

@@ -54,7 +54,7 @@ export function promiseFromEvent<T, U>(
 	let cancel = new EventEmitter<void>();
 	return {
 		promise: new Promise<U>((resolve, reject) => {
-			cancel.event(_ => reject());
+			cancel.event(_ => reject('Cancelled'));
 			subscription = event((value: T) => {
 				try {
 					Promise.resolve(adapter(value, resolve, reject))

src/vs/workbench/services/authentication/browser/authenticationService.ts

@@ -721,7 +721,7 @@ export class AuthenticationService extends Disposable implements IAuthentication
 
 		const didTimeout: Promise<MainThreadAuthenticationProvider> = new Promise((_, reject) => {
 			setTimeout(() => {
-				reject();
+				reject('Timed out waiting for authentication provider to register');
 			}, 5000);
 		});