title: RXJS throw error in a fromPromise does not hit 'catchError' piped method
body: <p>Can someone explain why this promise (runQuery) , which fails into the 'catch' and throws an ErrorObservable, does not get caught in the 'catchError' method, but goes into 'map' method.<br>
  ( I tried both _throw/ErrorObservable approach, same result )</p>
  
  <pre class="lang-js prettyprint-override"><code>import { _throw } from 'rxjs/observable/throw';
  import { ErrorObservable } from 'rxjs/observable/ErrorObservable';
  
  const runQuery = ( Promise that rejects )
  
  const source$ = fromPromise(
    runQuery({ d: 'g' })
      .catch(err =&gt; {
        return new ErrorObservable(err);
        //return _throw(err); -- same as above
      })
    )
    .pipe(
      map((response: any) =&gt; {
        //ENTERS HERE as response.error     
      }),
      catchError(e =&gt; {
        //DOES NOT ENTER
      })
    );
  </code></pre>