catch unhandled promise rejections in build

build/gulpfile.hygiene.js

@@ -229,6 +229,11 @@ gulp.task('hygiene', () => hygiene());
 if (require.main === module) {
 	const cp = require('child_process');
 
+	process.on('unhandledRejection', (reason, p) => {
+		console.log('Unhandled Rejection at: Promise', p, 'reason:', reason);
+		process.exit(1);
+	});
+
 	cp.exec('git config core.autocrlf', (err, out) => {
 		const skipEOL = out.trim() === 'true';
 

gulpfile.js

@@ -58,8 +58,14 @@ var ALL_EDITOR_TASKS = [
 	'tslint',
 	'hygiene',
 ];
+
 var runningEditorTasks = process.argv.length > 2 && process.argv.slice(2).every(function (arg) { return (ALL_EDITOR_TASKS.indexOf(arg) !== -1); });
 
+process.on('unhandledRejection', (reason, p) => {
+	console.log('Unhandled Rejection at: Promise', p, 'reason:', reason);
+	process.exit(1);
+});
+
 if (runningEditorTasks) {
 	require(`./build/gulpfile.editor`);
 	require(`./build/gulpfile.hygiene`);