lnonion: (trivial) make OnionPacket.__init__ kw-only

Author: SomberNight

electrum/lnonion.py

@@ -114,7 +114,7 @@ def __repr__(self):
 
 class OnionPacket:
 
-    def __init__(self, public_key: bytes, hops_data: bytes, hmac: bytes, version: int = 0):
+    def __init__(self, *, public_key: bytes, hops_data: bytes, hmac: bytes, version: int = 0):
         assert len(public_key) == 33
         assert len(hops_data) in [HOPS_DATA_SIZE, TRAMPOLINE_HOPS_DATA_SIZE, ONION_MESSAGE_LARGE_SIZE]
         assert len(hmac) == PER_HOP_HMAC_SIZE