// import { map } from 'rxjs/operators'; // Fails at runtime
import 'rxjs/add/operator/map'; // Works fine at runtime

  public login(username: string, password: string): Observable<any> {
    console.log('Sending the login credentials to obtain a token');
    const credentials = { 'email': username, 'password': password };
    return this.httpService.postWithHeadersInResponse(URI_LOGIN, credentials)
      .map((response: HttpResponse<any>) => {
        const header = response.headers.get(this.authService.getHeaderName());
        const token = this.authService.extractTokenFromHeader(header);
        console.log('The token from the response header: ' + token);
        this.authService.setJwtTokenToLocalStorage(token);
      });
  }