Raise a clear client error for a refused request

socket_comms now raises DaemonError with the server message if the reply has the status ERROR. Before, the reply reached code that expects device data, and that code raised KeyError.

tests/test_server.py

@@ -507,6 +507,21 @@ class TestServerMain:
         finally:
             self._stop_server(sock_path, t)
 
+    def test_unknown_command_is_a_clear_error_in_the_client(self, tmp_path):
+        """The real client, against a server that does not know the command."""
+        from bmspy import client
+
+        sock_path = str(tmp_path / "server_refused.sock")
+        ready = threading.Event()
+        t = self._make_server_thread(sock_path, ready, threading.Event())
+        t.start()
+        ready.wait(timeout=2)
+        try:
+            with pytest.raises(client.DaemonError, match="daemon refused 'NEWER': unknown command: 'NEWER'"):
+                client.socket_comms(sock_path, {"command": "NEWER", "client": "test"})
+        finally:
+            self._stop_server(sock_path, t)
+
     def test_devices_command_lists_configured_devices(self, tmp_path):
         """DEVICES names every configured device, through the real client."""
         from bmspy import client