Perform action when http resolves and throw error if needed

I'm trying to do the following with observables and I can't figure out what the best way would be to do it:

I'm calling a login endpoint using http. This service will return a token. I want to perform 2 different actions from 2 different points within the APP sequentially: when http resolves I need to store the provided token and then show a message. I tried the following:

return this.http.get(this.config.getApi('login'), params)
           .map(response => response.json())
           .do((data) => {
               // Store token here
               // If it fails, throw error
               // Tried Observable.throw here but the subscriber doesn't get it.
            }).subscribe(
               (data) => {
                  // Everything went fine
                },
               () => {
                  // Either the http request failed or 
                 // the process of storing the token threw an error.
            }
       );

Unfortunately, the subscribers to the returned observable never get error unless the http call fails. What operator should I use instead of do?

Thanks.