WIP: in_progress filesystem grows indefinitely - test

#3372368

src/Feeds/Fetcher/HttpFetcher.php

@@ -185,6 +185,10 @@ class HttpFetcher extends PluginBase implements ClearableInterface, FetcherInter
     }
     catch (RequestException $e) {
       $args = ['%site' => $url, '%error' => $e->getMessage()];
+
+      // Since the fetch is getting aborted, delete the downloaded file.
+      $this->fileSystem->unlink($sink);
+
       throw new \RuntimeException($this->t('The feed from %site seems to be broken because of error "%error".', $args));
     }