I just spoke to the upstream maintainer of hashed-storage. He told me that he was phasing out bytestring-mmap in favour of the more powerful (and Windows-compatible) mmap package.
If upstream makes a new release that doesn't use bytestring-mmap, I won't change this into an ITP. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org