`future-client-streams/get` returns no error code

[alexcrichton]

CI on Wasmtime just spuriously failed in this unwrap where the error came from this location. Unfortunately though there's no way to debug this as there's no error information. It's expected that hitting example.com won't always succeed but I'd also be curious to dig a bit more into the why of what's happening here.

Would it be possible to have some sort of error code get communicated to the guest to assist in debugging what's going on? We could orthogonally do something like log dropped errors on the host as well perhaps.

[badeend]

Fixed by #10