Improve debug message

Author: bouwew

plugwise_usb/network/__init__.py

@@ -150,7 +150,7 @@ def registry(self) -> dict[int, tuple[str, NodeType | None]]:
     async def register_node(self, mac: str) -> bool:
         """Register node to Plugwise network."""
         if not validate_mac(mac):
-            raise NodeError(f"Invalid mac '{mac}' to register")
+            raise NodeError(f"MAC '{mac}' invalid")
         address = await self._register.register_node(mac)
         return await self._discover_node(address, mac, None)