pkg/cvo/updatepayload: Context around ValidateDirectory calls

These usually either succeed or give os.IsNotExist, but in some cases
can return errors like [1]:

  Unable to download and prepare the update: stat /etc/cvo/updatepayloads/7WNaprXJNWTsPAepCHJ00Q/release-manifests/release-metadata: permission denied.

To make it easier to debug those situations, this commit adds context
to errors near ValidateDirectory calls, so it's more clear that the
issue is the CVO's attempts to read /etc/cvo/... failing, and not an
error with the version-... Pod, registry access, etc.

Also while I'm in this space, I've replaced the old errors.Wrap in
ImageForShortName with fmt.Errorf(...%w, ...), now that the Go
standard libraries support error-wrapping like that.  One fewer
3rd-party dependency call-site.

[1]: https://issues.redhat.com/browse/OCPBUGS-52258

Author: wking

pkg/cvo/updatepayload.go

@@ -173,15 +173,15 @@ func (r *payloadRetriever) targetUpdatePayloadDir(ctx context.Context, update co
 	if err := payload.ValidateDirectory(tdir); os.IsNotExist(err) {
 		// the dirs don't exist, try fetching the payload to tdir.
 		if err := r.fetchUpdatePayloadToDir(ctx, tdir, update); err != nil {
-			return "", err
+			return "", fmt.Errorf("fetching update payload: %s", err)
 		}
 	} else if err != nil {
-		return "", err
+		return "", fmt.Errorf("checking to see if %q already holds release-image content: %w", tdir, err)
 	}
 
 	// now that payload has been loaded check validation.
 	if err := payload.ValidateDirectory(tdir); err != nil {
-		return "", err
+		return "", fmt.Errorf("confirming the presence of release-image content in %q: %w", tdir, err)
 	}
 	return tdir, nil
 }

pkg/payload/image.go

@@ -3,22 +3,20 @@ package payload
 import (
 	"fmt"
 	"path/filepath"
-
-	"github.com/pkg/errors"
 )
 
 // ImageForShortName returns the image using the updatepayload embedded in
 // the Operator.
 func ImageForShortName(name string) (string, error) {
 	if err := ValidateDirectory(DefaultPayloadDir); err != nil {
-		return "", err
+		return "", fmt.Errorf("error validating %q as a release-image directory: %w", DefaultPayloadDir, err)
 	}
 
 	releaseDir := filepath.Join(DefaultPayloadDir, ReleaseManifestDir)
 
 	imageRef, err := loadImageReferences(releaseDir)
 	if err != nil {
-		return "", errors.Wrapf(err, "error loading image references from %q", releaseDir)
+		return "", fmt.Errorf("error loading image references from %q: %w", releaseDir, err)
 	}
 
 	for _, tag := range imageRef.Spec.Tags {