SystemJS making ~200 requests for non-existing files
<p>I'm really lost about this. When I load my Angular2 app, I have about 200 requests to my server for non-existing files under <code>node_modules/systemjs</code>. Here's a sample of of those requests:</p>

<pre><code>127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/Subject.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/Observable.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/root.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/toSubscriber.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/Subscriber.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/isFunction.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/Subscription.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/isArray.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/isObject.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/tryCatch.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/errorObject.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/UnsubscriptionError.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/Observer.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/rxSubscriber.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/observable.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/ObjectUnsubscribedError.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/SubjectSubscription.js.map HTTP/1.1" 404 -
127.0.0.1 - - [13/Sep/2016 13:00:06] "GET /node_modules/systemjs/dist/from.js.map HTTP/1.1" 404 -
</code></pre>

<p>My Angular2 application works fine, I don't get a single error, everything functions as expected. But those ~200 404 requests are really slowing down the page load. For a reason I really can't understand, those 404 requests don't even show up in my browser's <code>network</code> tab, but Wireshark confirms they are coming from there.</p>

<p>Here is my <code>systemjs.config.js</code>:</p>

<pre><code>/**
 * System configuration for Angular 2 samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    defaultJSExtensions: true,
    paths: {
      // paths serve as alias
      'npm:': 'node_modules/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      app: 'app',
      // angular bundles
      '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
      '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
      '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
      '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
      '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',
      // angular testing umd bundles
      '@angular/core/testing': 'npm:@angular/core/bundles/core-testing.umd.js',
      '@angular/common/testing': 'npm:@angular/common/bundles/common-testing.umd.js',
      '@angular/compiler/testing': 'npm:@angular/compiler/bundles/compiler-testing.umd.js',
      '@angular/platform-browser/testing': 'npm:@angular/platform-browser/bundles/platform-browser-testing.umd.js',
      '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic-testing.umd.js',
      '@angular/http/testing': 'npm:@angular/http/bundles/http-testing.umd.js',
      '@angular/router/testing': 'npm:@angular/router/bundles/router-testing.umd.js',
      '@angular/forms/testing': 'npm:@angular/forms/bundles/forms-testing.umd.js',
      // other libraries
      'rxjs':                       'npm:rxjs',
      'angular2-in-memory-web-api': 'npm:angular2-in-memory-web-api',
      'moment':                     'npm:moment/moment',
      'ng2-bs3-modal':              'npm:ng2-bs3-modal',
    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.js',
        defaultExtension: 'js'
      },
      rxjs: {
        defaultExtension: 'js'
      },
      'angular2-in-memory-web-api': {
        main: './index.js',
        defaultExtension: 'js'
      },
    }
  });
})(this);
</code></pre>