Pipeline: Avoid spamming stderr when not needed

This commit add a new DataError Variant for feeds that return 304.
Its expected behaviror and the current API of Source::into_feed
is kinda limiting the return type to make it easier to handle.

Up till now 304 was returning an Error to early return. Ideally
Source::into_feed will return a Multi variant Result Enum.

example:

enum FeedResult {
    Ok(Success(feed)),
    Ok(NotModified),
    Err(err),
}

Hopefully in a refactor in the near Future™

Till then we will just have to match and ignore
DataError::FeedNotModified.

podcasts-data/src/errors.rs

@@ -65,6 +65,8 @@ pub enum DataError {
     HttpStatusGeneral(HttpStatusError),
     #[fail(display = "Source redirects to a new url")]
     FeedRedirect(Source),
+    #[fail(display = "Feed is up to date")]
+    FeedNotModified(Source),
     #[fail(
         display = "Error occured while Parsing an Episode. Reason: {}",
         reason

podcasts-data/src/models/source.rs

@@ -144,7 +144,10 @@ impl Source {
         };
 
         match code {
-            StatusCode::NotModified => return Err(self.make_err("304: skipping..", code)),
+            StatusCode::NotModified => {
+                info!("304: Source, (id: {}), is up to date", self.id());
+                return Err(DataError::FeedNotModified(self));
+            }
             StatusCode::MovedPermanently | StatusCode::Found | StatusCode::PermanentRedirect => {
                 warn!("Feed was moved permanently.");
                 self = self.update_url(&res)?;

podcasts-data/src/pipeline.rs

@@ -38,8 +38,13 @@ where
         })
         // the stream will stop at the first error so
         // we ensure that everything will succeded regardless.
-        .map_err(|err| error!("Error: {}", err))
-        .then(|_| ok::<(), DataError>(()))
+        .map_err(|err| {
+            match err {
+                // Avoid spamming the stderr when its not an eactual error
+                DataError::FeedNotModified(_) => (),
+                _ => error!("Error: {}", err),
+            }
+        }).then(|_| ok::<(), DataError>(()))
         .collect()
 }