tests: cover 'Blob.download_as_string' when no hash matches (#284)
tests: cover 'Blob.download_as_string' when no hash matches (#284)


Co-authored-by: Tres Seaver <0c654242ef00c3b4e79f8f8068911d86fe01854e@palladion.com>
googleapis/python-storage,googleapis/python-storage