submarine_swaps: define main_loop, with async with taskgroup

rm unneeded @ignore_exception wrapper in lnworker and network

electrum/lnworker.py

@@ -309,7 +309,6 @@ class LNWorker(Logger, EventListener, NetworkRetryManager[LNPeerAddr]):
             except OSError as e:
                 self.logger.error(f"cannot listen for lightning p2p. error: {e!r}")
 
-    @ignore_exceptions  # don't kill outer taskgroup
     async def main_loop(self):
         self.logger.info("starting taskgroup.")
         try:

electrum/submarine_swaps.py

@@ -207,8 +207,17 @@ class SwapManager(Logger):
             self.add_lnwatcher_callback(swap)
 
         self.taskgroup = OldTaskGroup()
-        coro = self.pay_pending_invoices()
-        asyncio.run_coroutine_threadsafe(self.taskgroup.spawn(coro), self.network.asyncio_loop)
+        asyncio.run_coroutine_threadsafe(self.main_loop(), self.network.asyncio_loop)
+
+    async def main_loop(self):
+        self.logger.info("starting taskgroup.")
+        try:
+            async with self.taskgroup as group:
+                await group.spawn(self.pay_pending_invoices())
+        except Exception as e:
+            self.logger.exception("taskgroup died.")
+        finally:
+            self.logger.info("taskgroup stopped.")
 
     async def pay_invoice(self, key):
         self.logger.info(f'trying to pay invoice {key}')

electrum/wallet.py

@@ -452,7 +452,6 @@ class Abstract_Wallet(ABC, Logger, EventListener):
     def _init_lnworker(self):
         self.lnworker = None
 
-    @ignore_exceptions  # don't kill outer taskgroup
     async def main_loop(self):
         self.logger.info("starting taskgroup.")
         try: