The credential-cache helper will try to connect to its daemon over a unix socket. Originally, a failure to do so was silently ignored, and we would either give up (if performing a "get" or "erase" operation), or spawn a new daemon (for a "store" operation).
But since 8ec6c8d, we try to report more errors. We detect a missing daemon by checking for ENOENT on our connection attempt. If the daemon is missing, we continue as before (giving up or spawning a new daemon). For any other error, we die and report the problem.
However, checking for ENOENT is not sufficient for a missing daemon. We might also get ECONNREFUSED if a dead daemon process left a stale socket. This generally shouldn't happen, as the daemon cleans up after itself, but the daemon may not always be given a chance to do so (e.g., power loss, "kill -9").
The resulting state is annoying not just because the helper outputs an extra useless message, but because it actually blocks the helper from spawning a new daemon to replace the stale socket.