update message context

Author: guybedford

lib/internal/modules/cjs/loader.js

@@ -968,10 +968,10 @@ Module._extensions['.js'] = function(module, filename) {
     if (pkg && pkg.type === 'module') {
       if (warnRequireESM) {
         process.emitWarning(
-          'require() of .js files inside of a package with "type": "module" ' +
-          'in its package.json is not supported under --experimental-modules' +
-          '\nRather use import to load this module, or if you are the author' +
-          ' you may want to use the .cjs extension for this file.'
+          'require() of .js file ' + filename + ' is not supported as it is ' +
+          'an ES module due to having "type": "module" in its package.json ' +
+          'file.\nRather use import to load this module, or if you are the ' +
+          'author you may want to use the .cjs extension for this file.'
         );
         warnRequireESM = false;
       }

test/es-module/test-cjs-esm-warn.js

@@ -17,8 +17,8 @@ child.on('close', common.mustCall((code, signal) => {
   assert.strictEqual(code, 0);
   assert.strictEqual(signal, null);
   assert.strictEqual(stderr, `(node:${child.pid}) Warning: require() of .js ` +
-      'files inside of a package with "type": "module" in its package.json ' +
-      'is not supported under --experimental-modules\nRather use import to ' +
-      'load this module, or if you are the author you may want to use the ' +
-      '.cjs extension for this file.\n');
+      `file ${entry} is not supported as it is an ES module due to having ` +
+      '"type": "module" in its package.json file.\nRather use import to load ' +
+      'this module, or if you are the author you may want to use the .cjs ' +
+      'extension for this file.\n');
 }));