我发现如果你创建一个计算引擎（CentOS 或 Debian）机器并使用 gsutil 下载（cp）一个 tgz 文件会导致一个 crcmod 错误......
$ gsutil cp gs://mybucket/data.tgz .
Copying gs://mybucket/data.tgz...
CommandException:
Downloading this composite object requires integrity checking with CRC32c, but
your crcmod installation isn't using the module's C extension, so the the hash
computation will likely throttle download performance. For help installing the
extension, please see:
$ gsutil help crcmod
To download regardless of crcmod performance or to skip slow integrity checks,
see the "check_hashes" option in your boto config file.
目前我使用“check_hashes = …