Stop retrying pull on UnkownBlob error

Signed-off-by: Darren Stahl <darst@microsoft.com>

distribution/errors.go

@@ -6,6 +6,7 @@ import (
 	"syscall"
 
 	"github.com/Sirupsen/logrus"
+	"github.com/docker/distribution"
 	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/client"
@@ -139,6 +140,9 @@ func retryOnError(err error) error {
 	case *client.UnexpectedHTTPResponseError:
 		return xfer.DoNotRetry{Err: err}
 	case error:
+		if err == distribution.ErrBlobUnknown {
+			return xfer.DoNotRetry{Err: err}
+		}
 		if strings.Contains(err.Error(), strings.ToLower(syscall.ENOSPC.Error())) {
 			return xfer.DoNotRetry{Err: err}
 		}

distribution/pull_v2.go

@@ -189,9 +189,6 @@ func (ld *v2LayerDescriptor) Download(ctx context.Context, progressOutput progre
 	layerDownload, err := ld.open(ctx)
 	if err != nil {
 		logrus.Errorf("Error initiating layer download: %v", err)
-		if err == distribution.ErrBlobUnknown {
-			return nil, 0, xfer.DoNotRetry{Err: err}
-		}
 		return nil, 0, retryOnError(err)
 	}