tests: Add exception print to downloader_check test

This exception will help diagnose download errors when they occur by
printing the specific Exception thrown by the resource downloader.

Change-Id: Iab35f85fa305594076bf582228e89dae611ce8df
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61631
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

tests/gem5/configs/download_check.py

@@ -86,8 +86,10 @@ for id in ids:
     download_path = os.path.join(args.download_directory, id)
     try:
         get_resource(resource_name=id, to_path=download_path)
-    except Exception:
+    except Exception as e:
         errors += f"Failure to download resource '{id}'.{os.linesep}"
+        errors += f"Exception message:{os.linesep}{str(e)}"
+        errors += f"{os.linesep}{os.linesep}"
         continue
 
     if md5(Path(download_path)) != resource_json["md5sum"]: