pipeline: Make sure that the futures will be run.

Use .then() combinator to override the result and return
Ok(()) even if the task fails. That allows us to use join_all
instead of the custom written collect_futures function.

hammond-data/src/pipeline.rs

@@ -53,18 +53,16 @@ pub fn pipeline<S: IntoIterator<Item = Source>>(
     let list: Vec<_> = sources
         .into_iter()
         .map(clone!(client => move |s| s.into_feed(client.clone(), ignore_etags)))
-        .map(|fut| fut.and_then(|feed| feed.index()))
-        .map(|fut| fut.map(|_| ()).map_err(|err| error!("Error: {}", err)))
+        .map(|feed| {
+            feed.and_then(|f| f.index())
+                .map_err(|err| error!("Error: {}", err))
+                // join_all stops at the first error so
+                // we ensure that everything will succeded regardless.
+                .then(|_| ok::<(), DataError>(()))
+        })
         .collect();
 
-    if list.is_empty() {
-        return Err(DataError::EmptyFuturesList);
-    }
-
-    // Thats not really concurrent yet I think.
-    tokio_core.run(collect_futures(list))?;
-
-    Ok(())
+    tokio_core.run(join_all(list)).map(|_| ())
 }
 
 /// Creates a tokio `reactor::Core`, and a `hyper::Client` and