consistent error messaging for rejected promises

If a test is rejected with a non-Error reason an AssertionError is created.

Like when a non-Error is thrown, use inspect() to include a string
representation of the rejection reason.

Author: novemberborn

lib/test.js

@@ -161,7 +161,7 @@ Test.prototype.run = function () {
 				if (!(err instanceof Error)) {
 					err = new assert.AssertionError({
 						actual: err,
-						message: 'Promise rejected with "' + err + '"',
+						message: 'Promise rejected with: ' + inspect(err, {depth: null}),
 						operator: 'promise'
 					});
 				}

test/promise.js

@@ -318,7 +318,7 @@ test('reject with non-Error', function (t) {
 	}).run().then(function (result) {
 		t.is(result.passed, false);
 		t.is(result.reason.name, 'AssertionError');
-		t.is(result.reason.message, 'Promise rejected with "failure"');
+		t.is(result.reason.message, 'Promise rejected with: \'failure\'');
 		t.end();
 	});
 });