In the GridFS implementation, we should review how and when errno is set, as well as what promises we have made regarding errno in the public documentation.
Document that timeout_msec is unused in GridFS read/write
mongoc_gridfs_find_one_with_opts(): the error parameter is not initialized on failure
Given mongoc_gridfs_file_readv() returning -1 (failure), mongoc_gridfs_file_error() doesn't indicate error condition
Driver should check for missing GridFS file chunks