R108
A sidecar function panicked or returned an undeclared error (500). The detail stays in the sidecar's log, under the request id.
Fix: Find the request id in the sidecar's log, or declare the failure in errors.
Status in weft@0.1.0: reported by @weft-js/start when it serves or renders the route, and by weft check and weft routes --meta.