fix(events): cannot use tokens as event bus name (aws#10772)

added a condition to ensure that eventBusName does not contain
an unresolved token before performing validation.

Closes aws#10467


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-events/lib/event-bus.ts

@@ -1,5 +1,5 @@
 import * as iam from '@aws-cdk/aws-iam';
-import { IResource, Lazy, Resource, Stack } from '@aws-cdk/core';
+import { IResource, Lazy, Resource, Stack, Token } from '@aws-cdk/core';
 import { Construct } from 'constructs';
 import { CfnEventBus } from './events.generated';
 
@@ -163,7 +163,7 @@ export class EventBus extends Resource implements IEventBus {
         throw new Error(
           '\'eventBusName\' and \'eventSourceName\' cannot both be provided',
         );
-      } else if (eventBusName !== undefined) {
+      } else if (eventBusName !== undefined && !Token.isUnresolved(eventBusName)) {
         if (eventBusName === 'default') {
           throw new Error(
             '\'eventBusName\' must not be \'default\'',

packages/@aws-cdk/aws-events/test/test.event-bus.ts

@@ -1,6 +1,6 @@
 import { expect, haveResource } from '@aws-cdk/assert';
 import * as iam from '@aws-cdk/aws-iam';
-import { CfnResource, Stack } from '@aws-cdk/core';
+import { Aws, CfnResource, Stack } from '@aws-cdk/core';
 import { Test } from 'nodeunit';
 import { EventBus } from '../lib';
 
@@ -170,6 +170,18 @@ export = {
     test.done();
   },
 
+  'does not throw if eventBusName is a token'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+
+    // WHEN / THEN
+    test.doesNotThrow(() => new EventBus(stack, 'EventBus', {
+      eventBusName: Aws.STACK_NAME,
+    }));
+
+    test.done();
+  },
+
   'event bus source name must follow pattern'(test: Test) {
     // GIVEN
     const stack = new Stack();