errors: lazy load util in internal/errors.js

Backport-PR-URL: #19191
PR-URL: #18358
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>

Author: joyeecheung

lib/internal/errors.js

@@ -14,7 +14,13 @@ const messages = new Map();
 const { defineProperty } = Object;
 
 // Lazily loaded
-var util = null;
+var util_ = null;
+function lazyUtil() {
+  if (!util_) {
+    util_ = require('util');
+  }
+  return util_;
+}
 
 function makeNodeError(Base) {
   return class NodeError extends Base {
@@ -65,11 +71,11 @@ class AssertionError extends Error {
     if (message) {
       super(message);
     } else {
+      const util = lazyUtil();
       if (actual && actual.stack && actual instanceof Error)
         actual = `${actual.name}: ${actual.message}`;
       if (expected && expected.stack && expected instanceof Error)
         expected = `${expected.name}: ${expected.message}`;
-      if (util === null) util = require('util');
       super(`${util.inspect(actual).slice(0, 128)} ` +
         `${operator} ${util.inspect(expected).slice(0, 128)}`);
     }
@@ -104,7 +110,7 @@ function message(key, args) {
   if (typeof msg === 'function') {
     fmt = msg;
   } else {
-    if (util === null) util = require('util');
+    const util = lazyUtil();
     fmt = util.format;
     if (args === undefined || args.length === 0)
       return msg;