title: Access error response data when ResponseContentType.Blob is used
body: <p>I'm facing issue with making request of type <code>ResponseContentType.Blob</code> and getting error message in case of failed call.</p>
  
  <p>The code is pretty simple:</p>
  
  <pre><code> let headers = new Headers({'Content-Type': 'application/json'});
   let options = new RequestOptions({headers: headers, responseType: ResponseContentType.Blob});
  
   return this.http.post('url', data, options)
        .subscribe(res =&gt; ..., err =&gt; console.log(err.json()) /* the problem is here */);
  </code></pre>
  
  <p>So having fully clarify JSON as server response in case of error but I can't access it: <code>err.json()</code> returns <code>Blob {size: 194, type: "application/json"}</code> only data.</p>
  
  <p>How to access response data? I can't change <code>ResponseContentType</code>to smth else as I expect file in case of success request.</p>