Returns file statistics for a given path.

def stat(self, filename):
        """Returns file statistics for a given path."""
        # NOTE: Size of the file is given by ContentLength from S3,
        # but we convert to .length
        client = boto3.client("s3")
        bucket, path = self.bucket_and_path(filename)
        try:
            obj = client.head_object(Bucket=bucket, Key=path)
            return StatData(obj['ContentLength'])
        except botocore.exceptions.ClientError as exc:
            if exc.response['Error']['Code'] == '404':
                raise errors.NotFoundError(None, None, "Could not find file")
            else:
                raise