DiskHashError = &KeepError{500, "Hash mismatch in stored data"}
ExpiredError = &KeepError{401, "Expired permission signature"}
NotFoundError = &KeepError{404, "Not Found"}
+ VolumeBusyError = &KeepError{503, "Volume backend busy"}
GenericError = &KeepError{500, "Fail"}
FullError = &KeepError{503, "Full"}
SizeRequiredError = &KeepError{411, "Missing Content-Length"}