无法删除GAE文件

我试图在使用上传中断后删除文件

final FileService fileService = FileServiceFactory.getFileService();
fileService.delete(file);

但我得到:

java.lang.UnsupportedOperationException: File \/blobstore\/writable:AD8BvukH[...]qau-Bb7AD does not have a finalized name

当我尝试使用完成文件时

FileWriteChannel writeChannel = fileService.openWriteChannel(file, true);
writeChannel.closeFinally();

然后openWriteChannel()失败了

com.google.appengine.api.files.FinalizationException
[...]
Caused by: com.google.apphosting.api.ApiProxy$ApplicationException: ApplicationError: 101: 

ApplicationError 101的含义是什么？如何正确删除文件？