gitlab-ci: Cope with OBS slowdown

OBS 2.10 has just been deployed and we started hitting timeouts. Being more patient, does not seem to help.

In the meantime, skip OBS scanning by default unless the SKIP_OBS var is set to no.

Task: https://phabricator.apertis.org/T8880

storage_stats/src/repository.rs

@@ -88,22 +88,31 @@ async fn read_deb822_file<
     download: F,
     client: &'client Client,
     url: &'url str,
-) -> Result<T> {
-    let bytes = download(client, url)
-        .await
-        .with_context(|| format!("Failed to download {}", url))?;
-
-    let file = tokio::task::block_in_place(|| {
-        rfc822_like::from_bytes(&bytes[..])
-            .with_context(|| format!("Failed to parse {}", url))
-    })?;
+) -> Result<Option<T>> {
+    match lift_404(
+        download(client, url)
+            .await
+            .with_context(|| format!("Failed to download {}", url)),
+    )? {
+        Some(bytes) => {
+            let file = tokio::task::block_in_place(|| {
+                rfc822_like::from_bytes(&bytes[..])
+                    .with_context(|| format!("Failed to parse {}", url))
+            })?;
+
+            debug!("Retrieved repo file");
+            Ok(Some(file))
+        }
 
-    debug!("Retrieved repo file");
-    Ok(file)
+        None => Ok(None),
+    }
 }
 
 impl Repository {
-    pub async fn read_release(&self, client: &Client) -> Result<RepositoryRelease> {
+    pub async fn read_release(
+        &self,
+        client: &Client,
+    ) -> Result<Option<RepositoryRelease>> {
         read_deb822_file(Client::get, client, &format!("{}/Release", &self.url)).await
     }
 
@@ -111,7 +120,7 @@ impl Repository {
         &self,
         client: &Client,
         component: &str,
-    ) -> Result<Vec<SourcePackage>> {
+    ) -> Result<Option<Vec<SourcePackage>>> {
         read_deb822_file(
             get_maybe_compressed_file,
             client,
@@ -125,7 +134,7 @@ impl Repository {
         client: &Client,
         component: &str,
         arch: &str,
-    ) -> Result<Vec<BinaryPackage>> {
+    ) -> Result<Option<Vec<BinaryPackage>>> {
         read_deb822_file(
             get_maybe_compressed_file,
             client,