Include ISO URL in download error, make output slightly easier to read.

pkg/minikube/cluster/cluster.go

@@ -217,7 +217,7 @@ func createHost(api libmachine.API, config cfg.MachineConfig) (*host.Host, error
 
 	if config.VMDriver != "none" {
 		if err := config.Downloader.CacheMinikubeISOFromURL(config.MinikubeISO); err != nil {
-			return nil, errors.Wrap(err, "Error attempting to cache minikube ISO from URL")
+			return nil, errors.Wrap(err, "unable to cache ISO")
 		}
 	}
 

pkg/util/downloader.go

@@ -72,9 +72,9 @@ func (f DefaultDownloader) CacheMinikubeISOFromURL(isoURL string) error {
 		options.ChecksumHash = crypto.SHA256
 	}
 
-	fmt.Println("Downloading Minikube ISO")
+	fmt.Printf("Downloading Minikube ISO")
 	if err := download.ToFile(isoURL, f.GetISOCacheFilepath(isoURL), options); err != nil {
-		return errors.Wrap(err, "Error downloading Minikube ISO")
+		return errors.Wrap(err, isoURL)
 	}
 
 	return nil