fix(xs-worker): provide error message on vat creation failure

test-innerVat.js was sensitive to engine-specific messages for
ReferenceError. But it also showed that when the XS supervisor reports
an error in setBundle, the message was being censored before being
passed back to the kernel.

Author: dckc

packages/SwingSet/src/kernel/vatManager/manager-subprocess-xsnap.js

@@ -1,5 +1,5 @@
 // @ts-check
-import { assert, details as X } from '@agoric/assert';
+import { assert, details as X, q } from '@agoric/assert';
 import { ExitCode } from '@agoric/xsnap/api';
 import { makeManagerKit } from './manager-helper';
 
@@ -125,7 +125,8 @@ export function makeXsSubprocessFactory({
     if (bundleReply[0] === 'dispatchReady') {
       parentLog(vatID, `bundle loaded. dispatch ready.`);
     } else {
-      assert.fail(X`failed to setBundle: ${bundleReply}`);
+      const [_tag, errName, message] = bundleReply;
+      assert.fail(X`setBundle failed: ${q(errName)}: ${q(message)}`);
     }
 
     /**

packages/SwingSet/src/kernel/vatManager/supervisor-subprocess-xsnap.js

@@ -83,7 +83,7 @@ function managerPort(issueCommand) {
             report.result = encode(item);
           })
           .catch(err => {
-            report.result = encode(['err', f.name, err.message]);
+            report.result = encode(['err', err.name, err.message]);
           })
           .catch(_err => {
             report.result = lastResort;

packages/SwingSet/test/vat-admin/test-innerVat.js

@@ -45,10 +45,13 @@ test('VatAdmin counter test', async t => {
 test('VatAdmin broken vat creation', async t => {
   const c = await doTestSetup(t, 'brokenVat');
   await c.run();
-  t.deepEqual(c.dump().log, [
-    'starting brokenVat test',
-    'yay, rejected: Error: Vat Creation Error: ReferenceError: missing is not defined',
-  ]);
+  const { log } = c.dump();
+  t.is(log.length, 2);
+  t.is(log[0], 'starting brokenVat test');
+  t.regex(
+    log[1],
+    /^yay, rejected: Error: Vat Creation Error:.*ReferenceError.*missing/,
+  );
 });
 
 test('error creating vat from non-bundle', async t => {