fix: error handling for localhost

[zeeshan595]

Passing localhost does not work for hc sandbox running inside nix develop. Use 127.0.0.1 instead. Not sure if this change is needed maybe we can just update the docs to capture that

[jost-s]

Yes, I've come across that too and changed all the tests to use 127.0.0.1. It's to do with Node.js having changed the preferred DNS resolution from IPv4 to IPv6. localhost will therefore resolve to ::1, and if your happ isn't also using IPv6 which I suppose it isn't doing, then the address cannot be found.