flatpipes::util::BufReader::as_bytes_reader doesn't handle failure

[catamorphism]

XXX (now a FIXME) says: "This isn't correct if f fails". In code I'm about to commit, I'm moving this from flatpipes::util into std::io_util

[metajack]

This is still an issue.

[emberian]

Still relevant

[pnkfelix]

this is gone. closing.