add backup url option read_10x_h5 (#1296)
add backup url option read_10x_h5 (#1296)

Co-authored-by: Gökçen Eraslan <52587ee04876146257447143ba980267feb23edc@gmail.com>
Co-authored-by: Isaac Virshup <d9d96763d10860478ad8c9f5058054d5cd289745@gmail.com>
theislab/scanpy,theislab/scanpy