Inspect method should be readonly

Author: XmiliaH

lib/vm.js

@@ -44,6 +44,9 @@ const {
 const {
 	VMScript
 } = require('./script');
+const {
+	inspect
+} = require('util');
 
 const objectDefineProperties = Object.defineProperties;
 
@@ -365,6 +368,8 @@ class VM extends EventEmitter {
 			_allowAsync: {__proto__: null, value: allowAsync}
 		});
 
+		this.readonly(inspect);
+
 		// prepare global sandbox
 		if (sandbox) {
 			this.setGlobals(sandbox);