Safety check for cases when RenameFile tries to move a large object to a bucket with

a different location or storage class.

The situation when object.rewrite doesn't return done=true can occur when
1) the target bucket is in a different location or storage class
and
2) the object is relatively large
See comments for https://cloud.google.com/storage/docs/json_api/v1/objects/copy for details. This situations shouldn't happen in the TensorFlow scenarios, which typically
rename the object within the same bucket, but it's useful to have a safety
check with a meaningful failure message.
Change: 134004191