lnwatcher: unwatch deeply mined channels

reduces log spam generated by "REDEEMED" channels...

electrum/lnwatcher.py

@@ -160,7 +160,8 @@ class LNWatcher(AddressSynchronizer):
         self.channels[address] = outpoint
 
     async def unwatch_channel(self, address, funding_outpoint):
-        pass
+        self.logger.info(f'unwatching {funding_outpoint}')
+        self.channels.pop(address, None)
 
     @log_exceptions
     async def on_network_update(self, event, *args):
@@ -170,7 +171,8 @@ class LNWatcher(AddressSynchronizer):
         if not self.synchronizer:
             self.logger.info("synchronizer not set yet")
             return
-        for address, outpoint in self.channels.items():
+        channels_items = list(self.channels.items())  # copy
+        for address, outpoint in channels_items:
             await self.check_onchain_situation(address, outpoint)
 
     async def check_onchain_situation(self, address, funding_outpoint):
@@ -315,7 +317,7 @@ class WatchTower(LNWatcher):
         return self.network.run_from_another_thread(f())
 
     async def unwatch_channel(self, address, funding_outpoint):
-        self.logger.info(f'unwatching {funding_outpoint}')
+        await super().unwatch_channel(address, funding_outpoint)
         await self.sweepstore.remove_sweep_tx(funding_outpoint)
         await self.sweepstore.remove_channel(funding_outpoint)
         if funding_outpoint in self.tx_progress: