remove no-longer used GCS creds helpers

repo/blob/gcs/gcs_storage.go

@@ -3,17 +3,13 @@ package gcs
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
 	"net/http"
-	"os"
 	"strconv"
 	"time"
 
 	gcsclient "cloud.google.com/go/storage"
 	"github.com/pkg/errors"
-	"golang.org/x/oauth2"
-	"golang.org/x/oauth2/google"
 	"google.golang.org/api/googleapi"
 	"google.golang.org/api/iterator"
 	"google.golang.org/api/option"
@@ -246,24 +242,6 @@ func (gcs *gcsStorage) toBlobID(blobName string) blob.ID {
 	return blob.ID(blobName[len(gcs.Prefix):])
 }
 
-func tokenSourceFromCredentialsFile(ctx context.Context, fn string, scopes ...string) (oauth2.TokenSource, error) {
-	data, err := os.ReadFile(fn) //nolint:gosec
-	if err != nil {
-		return nil, errors.Wrap(err, "error reading credentials file")
-	}
-
-	return tokenSourceFromCredentialsJSON(ctx, data, scopes...)
-}
-
-func tokenSourceFromCredentialsJSON(ctx context.Context, data json.RawMessage, scopes ...string) (oauth2.TokenSource, error) {
-	creds, err := google.CredentialsFromJSON(ctx, data, scopes...)
-	if err != nil {
-		return nil, errors.Wrap(err, "google.CredentialsFromJSON")
-	}
-
-	return creds.TokenSource, nil
-}
-
 // New creates new Google Cloud Storage-backed storage with specified options:
 //
 // - the 'BucketName' field is required and all other parameters are optional.