title: HttpInterceptor refactor error message
body: <p>I have an HttpInterceptor and I'd like it to refactor my error to remove brackets.</p>
  
  <pre><code>@Injectable()
  export class AuthInterceptor implements HttpInterceptor {
  
    constructor(public auth: AuthProvider, public app: App, private global: GlobalVariablesProvider) {}
  
    intercept(request: HttpRequest&lt;any&gt;, next: HttpHandler): Observable&lt;HttpEvent&lt;any&gt;&gt; {
  
      return next.handle(request).do((event: HttpEvent&lt;any&gt;) =&gt; {
        if (event instanceof HttpResponse) {
  
        }
      }, (err: any) =&gt; {
        // modify err here?
      });
    }
  }
  </code></pre>
  
  <p>I can't seem to modify <code>err</code> directly and I'm not sure how to pass the error along after modifying it.  The modification I'd like to make to <code>err</code> is:</p>
  
  <pre><code>err.error.replace(/\[|]/, '')
  </code></pre>