Reduce BatchUpdateBlobs error log output
Context
Whenever BatchUpdateBlobs raises an exception, it dumps the entire request into the log like this. The output of this is extremely verbose because it spews out every single blob verbatim into the log. This can eat up log quota and could potentially pose a security risk.
While the actual blob data is unhelpful, being able to see the digests of the blobs to be uploaded is quite nice. A resolution to this ticket could potentially provide a function like printable_request_metadata
that can parse this information out of a BatchUpdateBlobs request.