How can I display errors that display in XCode in Ionic?

Ionic Framework ionic-v3
1

I have some network errors like this:

2019-07-25 13:20:33.436282-0500 Project[451:26234] TIC TCP Conn Failed [18:0x2827fd8c0]: 3:-9816 Err(-9816)

2019-07-25 13:20:45.061083-0500 Project[451:26235] Task .<0> HTTP load failed (error code: -999 [1:89])

I also setup an interceptor that I thought was going to catch and display any such error. It doesn’t display these errors:

intercept(
    req: HttpRequest<any>,
    next: HttpHandler,
  ): Observable<HttpSentEvent | HttpHeaderResponse | HttpProgressEvent | HttpResponse<any> | HttpUserEvent<any>> {

    req = req.clone({
      setHeaders: {
        Authorization: `Bearer ${token}`,
      },
    });

    return next.handle(req).pipe(
      tap({
        error: this.errorHandler,
      }),
    );
  }

  private errorHandler = (error: any): void => {
    if (error instanceof HttpErrorResponse) {
      const message = HTTPManager.getErrorMessage(error);

      this.alerts.showErrorMessage(message);
    }
  }