Wrap timestamp error to give better understanding of where the error …

…came from

downloader/downloader.go

@@ -4,6 +4,7 @@ import (
 	"crypto/md5"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -236,12 +237,12 @@ func (d *Downloader) downloadImage(item *LibraryItem, filePath string) error {
 	// close file to prevent conflicts with writing new timestamp in next step
 	output.Close()
 
-	//If timestamp is availabe, set access time to current timestamp and set modified time to the time the item was first created (not when it was uploaded to Google Photos)
+	//If timestamp is available, set access time to current timestamp and set modified time to the time the item was first created (not when it was uploaded to Google Photos)
 	t, err := time.Parse(time.RFC3339, item.MediaMetadata.CreationTime)
 	if err == nil {
 		err = os.Chtimes(filePath, time.Now(), t)
 		if err != nil {
-			return err;
+			return errors.New("failed writing timestamp to file: " + err.Error())
 		}
 	}