getHeroes (): Observable<Stuff[]> {
  return this.http.get(this.url)
                  .map(this.extractData)
                  .catch(this.handleError);
}

import 'rxjs/add/operator/catch';

import {Observable} from 'rxjs/Rx';

import { Observable } from "rxjs/Observable";
import { catchError } from 'rxjs/operators';
...

export class ExampleClass {
  constructor(private http: HttpClient) {
    this.http.request(method, url, options).pipe(map(res => res),
      catchError((err: HttpErrorResponse) => {
        ...
      }
    )
  }
  ...
}