Power on returned HTTP 500 with a ConnectionRefusedError traceback. A unix socket
file outlives the process that created it, so a killed QEMU left
/tmp/uvk5-qmp.sock behind; wait_for_socket only checked os.path.exists, returned
immediately, and the connect then failed. It now probes with a real connect, which
distinguishes "listening" from "leftover file".
Two related hardenings:
- power_on cleans up if connecting fails. Otherwise a half-started QEMU keeps
running untracked, holds the socket, and blocks the next power on -- which is
how one stale socket turned into a repeatable failure.
- The route reports a failed power action as 503 with the reason, instead of a 500
and a traceback the browser cannot display.
Three tests cover the stale socket, a real listener, and a path that never appears.
mckero
0b879227e5