excluir(codigo: number): Promise<void> {

 let headers = new HttpHeaders();
 headers = headers.set(
    'Authorization',
    'Basic YWRtaW5AYWxnYW1vbmV5LmNvbTphZG1pbg==');

 return this.http
   .delete(`${this.lancamentosURL}/${codigo}999`, { headers: headers } )
   .toPromise()
   .then( response => null)
   .catch(error => error);