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>
1 file changed